Weather 101 - What Clouds Tell Recreational Boaters

You wouldn't leave the dock without first checking the local weather forecast. You can get weather information from TV, radio, your VHF radio and on the Internet (see Safety Links above). While on the water, your VHF radio is the best source for weather warnings. Even so, at certain times of the year weather can change rapidly and you should continually keep a "weather eye" out, especially to the west, in order to foresee changes which might be impending.
Clouds are a tool you can use to predict or forecast weather. The type of cloud and direction of movement can warn you of weather changes that are imminent. Clouds are categorized by the altitude at which they appear and the shape that they take.
(This is not an in-depth study of clouds, but an attempt to simplify the subject for use by recreational boaters.)
Cloud Group Cloud Height Cloud Types
High Clouds = Cirrus Above 18,000 feet Cirrus
Middle Clouds = Alto 6,500 feet to 18,000 feet Altostratus
Low Clouds = Stratus Up to 6,500 feet Stratus
Clouds with vertical growth   Cumulus
It is helpful to remember the following definitions of cloud shapes:
cumulus5.jpg (2658 bytes) Cumulus meaning "heap, a pile, an accumulation"
stratus5.jpg (3159 bytes) Stratus meaning "spread out, flatten, cover with a layer"
stormcloud2.jpg (2474 bytes) Nimbus meaning "rainy cloud"
Variations of cloud types are created by combining the cloud's shape/description with the altitudinal names as a prefix or suffix.
Cirros (high) or Cirro can be used with cumulus (heap) to indicate a cirrocumulus or high, lumpy cloud. Cirrocumulus clouds, sometime called "mackerel skies", can indicate the approach of a hurricane in the tropics. It can also be used with stratus (flat, layered) as in cirrostratus to indicate a high, flat or layered cloud.
Alto can also be used with cumulus and stratus to indicate altocumulus and altostratus which are middle altitude lumpy clouds and middle altitude layered clouds respectively.
Nimbo or nimbus might be used with cumulus or stratus to indicate a cloud formation that is producing precipitation. These clouds could be either cumulonimbus which would be a lumpy, vertically-rising rain cloud or nimbostratus which would be a sheet or flat-looking rain cloud.
High clouds exist above 18,000 feet and are cirrus clouds.
cirrus.jpg (2106 bytes) Cirrus clouds are the most common of the high clouds. They are composed of ice and consist of long, thin, wispy streamers. Cirrus clouds are usually white and predict fair weather. Sometimes called mares tails, they stream with the wind. By watching the movement of cirrus clouds you can tell from which direction weather is approaching. The appearance of cirrus clouds usually indicates that a change in weather will occur within 24 hours.
cirrostratus.jpg (2244 bytes) Cirrostratus are sheetlike, thin clouds that usually cover the entire sky. The sun or moon can shine through Cirrostratus clouds. Cirrostratus clouds usually come 12-24 hours before a rain or snow storm.
cirrocumulous.jpg (1969 bytes) Cirrocumulus are small, rounded puffs that usually appear in long rows. They are usually white, but sometimes appear gray. Cirrocumulus are usually seen in the winter and indicate fair, but cold, weather. In the tropics, they may indicate an approaching hurricane.
Medium high clouds occupy altitudes of 6,500 feet to 18,000 feet. These clouds are called alto clouds. Alto clouds are used to predict weather changes in 6 to 12 hours.
altostratus9.jpg (2660 bytes) An Altostratus cloud usually covers the whole sky. The cloud looks gray or blue-gray. The sun or moon may shine through an Altostratus cloud, but will appear hazy. An altostratus cloud usually forms ahead of storms with continuous rain or snow.
altocumulus.jpg (2601 bytes) Altocumulus clouds are grayish-white with one part of the cloud darker than the other. Altocumulus clouds usually form in groups. If you see Altocumulus clouds on a warm, sticky morning, be prepared for thunderstorms by late afternoon.
Low clouds, called stratus clouds, are at altitudes up to 6,500 feet. These clouds form a solid sheet or layer of cloud mass.
stratus2.jpg (3278 bytes) Stratus clouds are uniform gray in color and almost cover the entire sky. Light mist or drizzle is sometimes associated with Stratus clouds.
stratocumulus.jpg (3331 bytes) Stratocumulus clouds are low, lumpy and gray. Most form in rows with blue sky visible in between. Precipitation rarely occurs with Stratocumulus clouds, however, in frontal weather they may turn to Nimbostratus.
nimbostratus.jpg (3293 bytes) Nimbostratus clouds are dark gray with a ragged base. Rain or snow is associated with Nimbostratus clouds.
Clouds with vertical growth
cumulus2.jpg (3420 bytes) Vertically developing clouds are the Cumulus type. These small, lumpy clouds are low "fair weather" clouds. However, as they develop vertically (by rising hot air) they may go from small, fair weather clouds to large, boiling, vertically-growing monsters called cumulonimbus.
cumulonimbus.jpg (3273 bytes) Cumulonimbus are generally known as thunderstorm clouds. High winds will flatten the top of the cloud into an anvil-like shape. Cumulonimbus are associated with heavy rain, snow, hail, lightning, and tornadoes. The anvil usually points in the direction the storm is moving.
If you still can't remember all of the cloud names and formations, you can always watch the clouds for two specific weather situations that indicate a high probability of a storm:
  1. A "lowering ceiling": This means that the height of cloud formations continues to get lower and lower, usually caused by a warm front. As the ceiling lowers you will see clouds in the following order:
  • Cirrus
  • Cirrostratus
  • Altostratus
  • Stratus
  • Nimbostratus - storm clouds!
  1. On the other hand, watch for cumulus (puffy) clouds that start to rapidly develop vertically to become cumulonimbus thunderstorm clouds. On hot and humid days, these storms occur over water as the radiant heat from the land absorbs moisture from nearby water and rises to produce thunderheads. These storms can also indicate a cold front and may be preceded by squall lines, a row of black storm clouds. Wind shifts unpredictably and accelerates dramatically. Lightning can occur for miles in front of a storm and after the storm appears to have passed.
Other things to look for that indicate an approaching weather change:
  • Weather changes generally come from the west so scan the sky with your weather eye, especially to the west.
  • A sudden drop in temperature and change in the wind (increasing winds and/or seas) often means that a storm is near.
  • If you have a barometer on your boat check it every two to three hours. A rapid drop in pressure means a storm is approaching.
  • Reduce speed and proceed with caution
  • Put on PFDs.
  • Close all hatches and ports.
  • Head for the nearest shore that is safe to approach and duck into the lee of land.
  • Put the bow into the wind and take waves at about a 40-45 degree angle.
  • Watch for other boats and floating debris.
  • Pump out bilges and keep dry.
  • Change to a full fuel tank.
  • If there is lightning, unplug electrical equipment and keep away from ungrounded metal objects.
  • Secure loose items which could be tossed about.
  • Keep everyone low in the boat and near the centerline.

Trailer Without Tears

SailboatIf you’re one of the legions of trailer sailors, you know the advantages of having your boat in your driveway or storage yard instead of in a slip or on a mooring. Storms are not likely to be a concern and bottom paint is of only academic interest.
With these conveniences though, are other concerns. Your boat spends most of its life on the trailer. Either just sitting there, or being pulled down the highway at speeds it was never intended to attain on the water. All this places stresses on your water toy that may not have been considered by the original designer. Fortunately, there are things you can do to make life on the road less traumatic for your hull, rig, and accessories.
The most important is to be certain that your trailer is right for your boat. This means that the capacity should be adequate not just for the boat, but all the "necessary" gear you’ve stuffed into it. Not only does the trailer have to carry the weight, but so do the tires. It’s very common for sailboat owners to put smaller wheels on their trailers to lower the rig and make it easier to launch. Smaller tires turn faster, wear more rapidly, and are subject to higher stresses than ones with a larger diameter. Will the smaller tires carry the load without overheating and shedding their treads? Check the load rating on the sidewall. A 50% safety margin is not too much. Often, a better quality tire will do the trick without going to larger wheels.
What about the trailer bunks? (those boards your boat rides on) Are they long enough to give the hull good support? Because the boat is on the trailer so much, a poorly supported hull can start to sag and show stress cracks in odd places. When the boat is off the trailer, take a good look at that old carpeting on the bunks. It’s not hard to replace, but you’ll have to give up some sailing after you launch and do some work with a big staple gun to replace the padding. Use some good indoor/outdoor carpet, and pre-cut it before you go to the lake. It’ll make the job go faster and you’ll be on the water in no time.
Getting back to the trailer, take a look at the ball on your hitch. Is it big enough? Does the size match the trailer tongue? The shank should be no more than 1/8 inch smaller than the hole in the hitch. Use the nut and lockwasher that came with the ball and tighten it to the manufacturer’s specifications. If the ball is at all suspect, replace it. A top-quality ball is less than $20 and thousands of dollars of boat are attached to it.
Trailer lights. I have never owned a trailer that didn’t give me problems with the lights sooner or later, mostly sooner. Electrical stuff was never meant to be dunked in the water. The best solution is to fabricate a light bar separate from the trailer that hangs on the stem of the boat. String a cable to the light plug on your tow vehicle and you have a system that will last for years, never be in the lake unless you forget to take it off before launching, and can be repaired without crawling around under the trailer.
If you’re using the lights mounted on the trailer, it’s a good idea to unhook them before launching. Cold water and hot lights do not co-exist well.
If you don’t have a set of bearing buddies that allow you to lubricate the wheel hearings without disassembling them, install a set. Give them a small shot of waterproof grease before every trip. If a bearing starts to go, you might not hear it and your first warning will be when it collapses and the boat and trailer go crazy at 60 mph. This does not make for a happy day.
If your boat weighs under a thousand pounds, it should be secured to the trailer. The easiest way is a webbing strap with a ratcheting adjustment. You might think that a five- or six-hundred pound boat won’t come off the trailer, but I’ve seen daylight under some pretty large craft when the trailer wheels hit a bump at speed. The strap is only about $20, so protect your investment.
Take a look at how everything else is secured for towing. Is you mast supported in at least three places? The flexing an aluminum mast can do on the road can cause enough metal fatigue to ensure a failure, always right when you need it the least. But then, who ever needed a mast to break?
Ensure that all the shrouds and rigging are held with ties or bungees so they won’t drag or catch on a passing semi. I like to use two bungees in each location. They have been known to break.
While you’re securing things, look at all the equipment on the boat. Will it stay in place in an 80 mph wind? I know you’d never drive that fast, but if you get a head wind or a gust from meeting a truck, things can become detached. Some of these might be vital to your sailing day. I once had a turnbuckle fall off the forestay on the way to the lake. Luckily, I had a spare. Now, I keep these things secured. I met another sailor who arrived without his mast. He had no idea where he lost it and was many miles from a replacement. When in doubt, stow items inside the boat or car.
The outboard motor should almost never be left on its bracket when towing. There are 40 pounds or more cantilevered out from your transom. When you hit a bump, the resulting loads can rip the bracket from the transom, leaving chunks of boat and motor parts on the highway. Anyone behind you will not be happy to see your Evinrude bouncing down the road at them. Nor will your insurance company.
You do have insurance, don’t you? Some auto policies cover your boat while you’re towing it, but it’s better to check. Insurance companies are in business to collect premiums, not to pay claims.
A cheap form of insurance is a spare tire. You think that’s obvious? How many times have you seen a trailer parked along the road with one wheel off while the owner drives into town to have a flat fixed? Anyone with a spare can take your boat for an extended vacation without you.
Make sure your jack works on the trailer as well as on your car. Many either won’t fit or don’t have the capacity. A small hydraulic jack likely will fit both needs better than the one that came with your car. It’s probably easier to use, too.
For many sailors, the hardest part of trailering is backing up. You don’t have to be a master truck driver to do this. You do need to remember a few simple rules. The most important of which is, you have to be able to see the trailer. This might mean putting extended mirrors on the tow car. These are available at automotive stores and can have either permanent or temporary mountings. For very low trailers you may want to add a couple of bright fiberglass poles so you can see it when the boat isn’t on it. These can be available from bicycle stores for a few dollars each.
To back the trailer, remember to GO SLOW. More people get into trouble trying to rush than for any other reason. Place both hands at the bottom of the wheel and move them in the direction you want the rear of the trailer to go. With this method, it doesn’t matter if you’re looking out the back window or in the mirrors. Take your rig to an empty parking lot and practice backing it into different areas. Most single-axle trailers turn and back easier than double- or triple-axle rigs. The two-wheel trailers do have a tendency to turn very sharply once they start, so back them even more carefully. Above all, don’t be reluctant to pull forward and start over if a backing operation is going badly. Trying to turn a bad start into a good finish often results in dents or other disasters.
Finally, keep your perspective. The fate of western civilization does not hang on your hitch.
Two wrongs don’t make a right, but three rights make a left.

 By Jim Smith

America’s Cup Seems All Over but the Sailing

Jim Wilson/The New York Times
As it has in most of the races in the America’s Cup, Emirates Team New Zealand, right, finished ahead of Oracle Team USA.
SAN FRANCISCO — Beaten again, James Spithill, the hard-driving skipper for Oracle Team USA, stood on his team’s catamaran Wednesday — with rough water and the Bay Bridge for a backdrop — and answered questions through a headset.
John G. Mabanglo/European Pressphoto Agency
New Zealand fans cheered on Emirates Team New Zealand before Wednesday’s 15-second victory against Oracle Team USA in San Francisco Bay.

“It’s not over; it’s a long way from over,” Spithill said.
That seemed much closer to bravado than to reality, with Emirates Team New Zealand needing only one more victory to dispossess Oracle of the America’s Cup and with Race 12 just about to begin.
But there are other forces at work in San Francisco Bay beyond crew work and technology worthy of nearby Silicon Valley. There are the wind limits put in place in the wake of the sailor Andrew Simpson’s accidental death in May. Those wind limits canceled both scheduled races Tuesday, then forced the second race to be postponed Wednesday with the big yachts already jousting for position and heading for the starting line.
No, the America’s Cup is still not over, even though it now seems only a matter of when, not if, the Kiwis will finish off Spithill and his multinational crew and their billionaire owner, Larry Ellison.
Wednesday’s postponement came after Team New Zealand had won the day’s first race by 15 seconds to take an 8-1 lead in the Cup. The hundreds of New Zealanders gathered on shore at America’s Cup Park and perhaps as many as a million more watching back home on morning television were poised for a celebration that has been a decade in the making for the nation of 4.4 million.
Now the Kiwis must wait until at least Thursday, when two more races are scheduled, either of which could be the final race.
“We can’t sit back and try to play it safe,” said Ray Davies, Team New Zealand’s tactician. “We’ve got to sail every race as best we can and push the boat really, really hard. You really notice it. As soon as you back off a little bit on these boats and try to go a bit conservative, your leads can get chopped down really quick.”
Davies and the Kiwis balanced risk and reward quite nicely in Wednesday’s first race, taking advantage of their favored port entry in the strong ebb tide that has complicated this week’s racing and also made the wind limits even lower.
Team New Zealand had the lead at the starting line, and then, with the two boats overlapped, used its right of way to force Oracle to drop speed. It then sailed away with a clear lead that was three seconds at the first mark.
But these AC72s, capable of hydro-foiling and hitting speeds well over 40 knots, are remarkably close in performance at this stage, and Oracle remained in close touch on the downwind leg. Team New Zealand’s lead was only six seconds at the second rounding mark, and Oracle even took the lead briefly on the upwind leg that followed.
But the Kiwis controlled the top of that leg beautifully. A mediocre tack from Oracle contributed to significant separation and a 17-second lead at the third mark. The gap grew bigger until Oracle, sailing alone and close to the boundaries of the course, began to make serious gains downwind.
But Davies and his team were thinking big picture, trying to avoid extra jibes that could have slowed their own progress. Spithill and the two Olympic gold medalists in his afterguard — Tom Slingsby and Ben Ainslie — could never conjure a way to get back in front, as the Kiwis, responding with just a hint of desperation, held them off and rounded with an 18-second lead before closing out their latest hard-fought victory.
“To have, in the first generation of the class, two boats that are this close in performance over a wide variety of conditions is quite unbelievable,” said Dean Barker, Team New Zealand’s understated skipper. “I think both teams have reacted very well to what they’ve observed of the other team, and I think the boats have just come together in terms of performance.”
But though the races have become tight and compelling, the gap in the standings keeps increasing. Team New Zealand has won eight races to Oracle’s three, but because of a two-race penalty imposed on Oracle for cheating before the Cup match began, the official score is 8-1.
“Look, we’ve got a hell of a battle on our hands here, but stranger things have happened in sport,” Spithill said. “I’ve witnessed some pretty big comebacks.”
There is no precedent for a comeback of this magnitude in the America’s Cup, which dates to 1851. And the prospect of losing the Cup hardly seems to have San Franciscans up in arms, clamoring for more speed from Oracle Team USA, a team that has only one American in its starting crew of 11.
“I’d love to see the Kiwis, the little underdogs, that tiny little country that has more sheep than people, take down Larry Ellison,” said Mike Altman, a 35-year-old American from San Francisco who was following the racing from America’s Cup Park on Wednesday.
Altman added: “Larry’s got a big ego, and you know I feel like he’s not necessarily the most well-liked business leader around the area. He hasn’t made a lot of friends. He’s known as pretty brash. A lot of people see this as his own personal party, his own little ego trip, and it’s not something that I think a lot of people were clamoring for, to have an America’s Cup here.”
Now it is likely to soon be gone, possibly never to return. In 162 years of the Cup, only eight sites have staged the races. One of them was Auckland, New Zealand, in 2000 and 2003.
No matter what Spithill says into his headset, a return visit looks imminent.

International boating rules

Distress signals
Distress signals must be used only to indicate need of assistance. Misuse of them may put the lives of others at risk and is illegal.

The following signals may be used to indicate distress.
1. Rockets or shells that throw red stars, fired into the air one at a time at short intervals.

2. A signal:
·       made by radiotelegraphy or by any other signalling method consisting of the letters S O S in Morse Code (••• - - - •••)
·       sent by marine radio consisting of the spoken word: mayday.
3. A square flag having above or below it a ball or anything resembling a ball.
4. A rocket parachute flare or a hand-held flare showing a red light.
5. A smoke signal giving off orange-coloured smoke.
6. Slowly and repeatedly raising and lowering arms outstretched to each side.
7. A rectangle of international orange-coloured material with either a:
·       black letter V
·       black square and circle, or
·       dye marker.
Short Blast - about one second duration
Description: hort blast
Prolonged Blast - four to six seconds duration
Description: ong blast
I am altering my course to starboard.
Description: hort blast
One short blast on a horn or similar device.
I am altering my course to port.
Two short blasts on a horn or similar device.
I am operating astern propulsion (Engines in reverse - vessel slowing down, stopping or intends going astern).
Three short blasts on a horn or similar device.
Signal by vessel in doubt as to the intentions of the other vessel.
Description:,%20travel%20and%20motoring/Marine/MarineSafety%20images/short_blast.jpgDescription:,%20travel%20and%20motoring/Marine/MarineSafety%20images/short_blast.jpgDescription:,%20travel%20and%20motoring/Marine/MarineSafety%20images/short_blast.jpgDescription:,%20travel%20and%20motoring/Marine/MarineSafety%20images/short_blast.jpgDescription:,%20travel%20and%20motoring/Marine/MarineSafety%20images/short_blast.jpgFive short blasts on a horn or similar device.
Vessel nearing a blind bend in a channel or river.
Description: ong blast
One long blast on a horn or similar device.
8. The International signal of distress indicated by N.C.

international distress signal

9. Continuous sounding of any fog-signalling apparatus.

10. Signal transmitted by an Emergency Position Indicating Radio Beacon (EPIRB).

Manoeuvring and warning signs

Large vessels sound a series of specific signals to indicate their intentions to other vessels in the vicinity. Some of the more common signals are listed below. 

Diver below flag

The signal flag for the letter A shown below is used internationally to indicate: I have a diver below - keep well clear at slow speed. 

The flag is coloured white and blue and may be displayed either from a vessel or floating buoy. It is an offence in South Australia to exceed four knots within 50 metres of a vessel or buoy displaying this flag. 

diver below flag

Navigation lights
Vessels underway at night must show navigation lights. Navigation lights indicate the:
  • presence of a vessel
  • approximate direction of travel
  • type of the vessel ie - power-driven or sailing.
Small rowing and sailing boats
Small rowing and sailing boats are the only vessels that don’t need navigation lights when operating at night, but operators of these vessels must instead carry a torch or lantern showing a white light and show it in sufficient time to prevent a collision.
Under 12 metres in length
Vessels under 12 metres in length use the following lights in various combinations, depending on whether the vessel is sail or power-driven, underway or at anchor.
navigation lights

Masthead light
Stern light
All-round light
Angle of visibility 
Range of visibility
(nautical miles)

As with channel and other lateral markers, the green sidelight indicates starboard and red indicates port, when looking in the direction of travel.
Power-driven vessels while underway
 Power-driven vessels while underway must show either:
  • a masthead light, separate or combined sidelights and a sternlight or
  • a white light visible all round and separate or combined sidelights, provided that the all-round white light is positioned so as not to interfere with the operator's vision.
power driven vessels underway

The masthead or all-round white light must be a minimum of one metre above the sidelights.
Sailing vessels while underway
Sailing vessels while underway must show:
  • separate or combined sidelights and a sternlight or
  • a single, tri-colour lantern, fixed to the masthead.
sailing vessels underway
Vessels at anchor: sail or power-driven
Vessels at anchor, either sail or power-driven, must show a single white light visible all round.
vessels at anchor
Dredge signals
Vessels undertaking dredging, diving or underwater operations display either two black diamonds in daylight hours or two green lights at night to indicate the side on which it is safe for other vessels to pass. This is the only time when red and green lights may not indicate a vessel’s direction of travel.

A dredge also displays either two black balls in daylight hours or two red lights at night on the side where dredging is taking place – to indicate where it's unsafe to pass.
dredge at night
dredge by day

Giving way
If you are required to give way to another vessel, take early and positive action so that your intentions are clear. Avoid making a series of small changes in speed or course that may not be apparent to the other vessel.

If another vessel is required to give way to you, maintain your present speed and course unless it is obvious that a collision may occur. In this case stop, slow down or turn away.
Rivers and channels
All vessels – including sail vessels – must always be navigated on the right (starboard) side of a river or channel in the direction of travel.
rivers and channels

Power-driven vessels crossing
If a vessel approaches on your right (starboard) side you must stop, slow down or change course so as to keep out of its way.
If a vessel approaches on your left (port) side, it should give way to you. Maintain your present speed and course unless it appears that a collision may occur.
power driven vessels crossing

Sailing and power-driven vessels crossing
Powered vessels normally give way to sail. However, in harbours and channels where there is restricted room, small sailing vessels must give way to large powered vessels that cannot easily manoeuvre. Similarly, sailing vessels must also give way to other vessels that are restricted in their ability to manoeuvre, including fishing vessels that may have nets or other equipment over the side.
sail and power driven vessels crossing

Power-driven vessels meeting head-on
Each vessel must alter course to the right (starboard) so as to pass on the port side of the other.
power driven vessels head on

Vessels overtaking
An overtaking vessel (including a sailing vessel) may pass on either side if safe, but must keep well clear of the vessel being overtaken.
vessels overtaking

Lateral marks
Lateral Marks are usually positioned to define well-established channels and indicate port and starboard sides of the navigation route into a port.
navigating lateral marks
 lateral marks port
Port mark is coloured red and the basic shape is a can.

lateral mark starboard
Starboard mark is coloured green and the basic shape is conical.

By night a port buoy shows a red light and a starboard buoy shows a green light.

Cardinal marks
A cardinal mark indicates where the safest water may be found and is best used together with a compass. It shows where the mariner can safe pass safely and may:
  • indicate the deepest water in an area
  • show the safest side to pass a danger
  • draw attention to a feature in a channel such as a bend, junction or an end of a shoal.
cardinal marks
Think of a clock face when remembering the lights on cardinal marks.  Three flashes for east, six flashes for south and nine flashes for west.
By day the colour scheme can be remembered by noting that the black segment is positioned where the cones point.
  • North – the top mark points up and black segment is at the top
  • East – the top marks point outward and there are black segments top and bottom
  • South – the top mark points downward and the black segment is at the bottom
  • West – the top marks point inward and the black segment is in the middle.

Top marks

Black double cones, clearly separated.

Colours - black and yellow horizontal bands with the position of the black band or bands relative to the respective cardinal points.

 Description: op mark north
Top mark points up, black band above yellow band.
 Description: op mark east
Top mark points outward, black bands above and below yellow band
 Description: op mark south
Top mark points down, black band below yellow band.
 Description: op mark west
Top mark points inward, black band between yellow bands.

Channel markers

Channel markers indicate the port and starboard limits of a narrow channel that has been dredged in a river or the approaches to a harbour to allow safe passage of large vessels. 

The waters outside the channel may be shallow or conceal rocks and other hazards to navigation. Navigating outside the marked channel could result in a vessel running aground and sustaining serious damage. 

Entrances to harbours or breakwaters may utilise different distinguishing characteristics, for example, white flashing lights. Please seek advice from the local marine authority.

Types of markers

Two types of marker are used to indicate the port and starboard limits and these may be either fixed or floating: see picture.
channel marks
The positioning of the two types of marker is determined by the general direction taken by a vessel when entering a harbour or proceeding upstream. 

Under this convention a vessel entering, for example, the Port Adelaide River would keep the port (red) markers on her port side and the starboard (green) markers on her starboard side. 

When leaving the harbour or proceeding downstream the situation is reversed, meaning that the port markers should now be passed on the vessel’s starboard side and vice-versa.

Isolated danger marks
Isolated danger marks are placed on, or moored above, an isolated danger of minimal area below the water around the mark. The water around the mark is safe to navigate. The colours are red and black horizontal stripes and the mark is, when practicable, also fitted with a black top mark of two vertically aligned spheres.

Isolated danger marks are not always positioned centrally over a danger so to be safe do not pass too close to the mark.
If the mark is lit, the light will be white showing a group of two flashes.  Two white flashes of light = two spheres.

Safe watermarks
Safe water marks show that there is navigable water all around the mark and can be used as a centre line, mid-channel or landfall buoy.
The shape of the buoy is spherical, pillar or spar (a round pole shape) and is coloured with red and white vertical strips. The top mark that's fitted when practicable to pillar and spar buoys, is spherical and red.

If lit, it shows an isophase occulting or single long flashing white light. An isophase is a special class of light which alternates eclipses and flashes of exactly equal duration. The buoy shape is optional but should not be in conflict with the buoy used for a lateral or special mark.
safe water marks

Operators of vessels are cautioned that large commercial vessels may pass close by these marks.

Port closed or channel blocked signal

The port closed or channel blocked signal is used to indicate a thoroughfare to navigation that's blocked. The signal may come from a shore station or from any vessel that's blocking the channel.
 port closed day
The marks are made up of three black shapes in a vertical line. The highest and lowest of these shapes shall be a ball and the middle on a cone with apex upwards.
port closed night

Three all round lights in a line where they can be best seen. The highest and lowest of these lights shall be red and middle light shall be green.

Channel blocked signals are increasingly likely to be seen in the River Murray and lakes as the ongoing effects of low water levels cause restrictions to some areas of water.

Day marks
Day marks are shown by day in all weathers on boats to denote certain situations that may limit the vessel’s ability to respond to other vessels, including when visibility is restricted, and must be recognised by vessel operators.
Vessel is restricted in its ability to manoeuvre

daymark restricted manoeuvring

Black ball, black diamond and black ball.
For example boats engaged in cable laying, replenishment at sea, underwater operation, servicing navigation marks or towing, where towing affects the manoeuvrability.

When at anchor, vessel also shows anchor shape. This signal does not indicate distress or a need for help.
Vessel at anchor
vessel at anchor
One black ball.
Located forward, where best seen.
Not required for boats of less than seven metres. Used when at anchor not in a channel or channel approach, or a usual anchorage.
Vessel under power with sails set
daymark under power with sails
One black cone, point down.
Located forward, where best seen.
Power-driven vessel towing another vessel
daymark powered vessel towing
towing measurement

One black diamond on each vessel where best seen if length of tow exceeds 200 metres. 

Vessel aground
daymark vessel aground
Three black balls.
Located where best seen, but not required for boats of less than 12 metres. This signal does not indicate distress or a need for help. 
Vessel not under command
daymark vessel not under command
Two black balls.
Located where best seen. Not required for boats of less than 12 metres. Indicates an inability to manoeuvre, but does not signal distress or a need for help. 
Boats fishing
daymark fishing vessels
Two black cones.
Indicates trawls, nets or other gear - underway or at anchor, point inwards. If fishing vessel is less than 20 metres, she may instead show a basket. 
Vessel constrained by her draught
daymark vessel constrained by draught
One cylinder.
Located where best seen indicates a power-driven vessel restricted to a narrow channel by her draught and therefore unable to deviate from course.