Lesson 9 of 13 · Module 3 — Close to land

Anchoring and mooring buoys

Choosing the spot, the seabed and Posidonia, scope and swinging room, checking the anchor holds, lines ashore and mooring buoys.

Day Skipper18 minVideo · Notes · Interactive · Exercises

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0:00 / 5:34Chapter 1 of 9: A night at anchor

Transcript

A quiet night at anchor in a clear bay is one of the best things about a charter. This lesson covers how to choose the spot, how much chain to let out, and how to know the anchor is holding. Then we take a line ashore, and pick up a mooring buoy.
Choose the anchorage over breakfast, with the chart and the pilot book open. First, shelter: the bay must be protected from the wind that is forecast, tonight as well as now. Second, depth: somewhere between about three and twelve metres is comfortable for a charter yacht. Third, the seabed: the chart and the pilot book tell you whether it is sand, mud, weed or rock. Fourth, room to swing, clear of rocks, swimming areas and the boats already there. On the practice chart, Kerran Roads is sheltered from southerly winds, but wide open to the north.
Sand is the best holding, and mud is good too. Weed is poor: the anchor skates over it, or pulls up a clump and drags. In the Mediterranean the weed is often Posidonia, a seagrass that grows in dark meadows on the seabed. It is protected, and in parts of the Mediterranean, such as the Balearics, anchoring on it can bring a heavy fine. So look down through the clear water, and drop the anchor on a light, sandy patch. Rock and coral are no good at all: the anchor cannot dig in, and coral is easily destroyed.
The length of chain you let out is called the scope. Measure the depth from the bow roller, so add the height of the bow, about a metre, to the depth of the water. In settled weather, let out four to five times that depth. If wind is forecast, let out more: seven times, if you have the room. So in eight metres of water, eight plus one is nine, and five times nine is forty-five metres of chain. The chain is often marked with paint or coloured tags every ten metres, so ask at the briefing what the colours mean. And check how much chain the boat carries, because a deep bay can take all of it.
Brief the crew and agree hand signals, because the helm cannot hear the bow over the engine. Approach slowly, head to wind, and stop where you want the anchor to lie. Lower the anchor to the seabed, then let the boat drift or motor gently astern as the chain runs out. Never dump the chain in a heap on top of the anchor. At about three times the depth, pause, and let the chain come taut so the anchor bites. Then let out the rest, and go astern firmly for a minute to dig it in. Last, put on the snubber, a rope bridle that takes the load off the windlass.
While you go astern, and again after an hour, check that the anchor is holding. Pick a transit abeam: two things ashore, one behind the other, such as a chapel and a rock on the shore. If they stay in line, you are not moving, but if they open up, you are dragging. The plotter track helps too: a boat at anchor draws a neat arc, a dragging boat draws a line. Set an anchor alarm on the plotter or a phone, measured from where the anchor went down, not from where the boat is. If it drags, do not argue with it: lift the anchor and try again, somewhere else if need be.
A boat at anchor swings around it as the wind changes, so it needs a circle of clear water. The radius is about the length of chain plus the length of the boat. With forty metres of chain on a twelve metre boat, that is fifty-two metres in every direction. Other boats swing too, so drop where you will lie like your neighbours, not on top of their anchor. The first boat in has the spot, so leave room around the boats already there. Then check your circle reaches no shallows, rocks or swimming areas, even if the wind swings right round in the night.
In narrow coves in Croatia, Greece and Turkey there is no room to swing, so boats take a line ashore. Drop the anchor well out, then reverse towards the shore, letting out chain. A crew member takes a long floating line ashore by dinghy, or swims it, and passes it round a rock, a tree or a ring. Bring the end back to the boat, so you can let go from on board. Then tighten the chain, so the boat sits between the anchor and the shore and cannot swing. Stern-to on a town quay, the Med mooring, works much the same way, with the quay in place of the tree.
Many bays now have mooring buoys instead, and in some you must use them. In Croatia, paid buoy fields fill the popular bays, and someone comes by in a boat to collect the fee. In the British Virgin Islands, the National Parks moorings are for day use, with a permit and a time limit. Approach slowly into the wind, or the way the other boats are lying, with a crew member at the bow pointing at the buoy. Pick up the line on the buoy with the boat hook, pass your own line through its loop, and bring both ends back to a cleat. Check the buoy is meant for a boat your size, and never tie up to a private buoy without asking. Next, the rules of the road.

In this lesson you will learn

Choose an anchorage from the chart, the pilot book and the forecast: shelter, depth, seabed, room and other boats
Work out the scope for the depth, bow height, tide and forecast, and the swinging room it needs
Drop and set the anchor, and check it holds with a transit, the plotter track and an anchor alarm
Take a line ashore, and pick up mooring buoys in Croatia, the British Virgin Islands and elsewhere

Choosing an anchorage

A good night at anchor is decided in the morning, with the chart and the pilot book open. The pilot book shows the bays with an anchor symbol, says what the bottom is and which winds they are open to; the chart shows the depths and the rocks. Check five things:

Check	What you want	Where to look
Shelter	Land between you and the wind that is forecast, tonight as well as now. A swell can arrive from a wind far away.	The forecast, and the pilot book's “open to” notes
Depth	About 3 to 12 m for a charter yacht: enough under the keel, not so deep you run out of chain	The chart's soundings and contours; the sounder on arrival
Holding	Sand or mud. Not weed, seagrass, rock or coral	The chart's seabed letters (S, M, Wd, R), the pilot book, and your eyes
Room to swing	A clear circle round the anchor, away from rocks, swimming areas and moorings	The chart, then a look round the bay
Other boats	Space between you and the boats already there	Arrive early in high summer: the best spots go by mid-afternoon

On the practice chart, the anchor symbol off the north of the island is Kerran Roads. The island shelters it from the south, but it is wide open to the north: a lovely spot in a southerly, and the wrong place to be when a northerly is forecast.

InteractiveKerran Roads on the practice chart

Pick the anchorage to zoom in on it, then the harbour, and compare which winds each is open to.

Choose a feature to zoom in on it. Use + / − to zoom yourself, and drag to move around.

The seabed: sand good, seagrass bad

Seabed	Holding	Notes
Sand	Good	Shows as light turquoise patches in clear water. The best place to drop.
Mud	Good	Common in Phang Nga Bay in Thailand and some sheltered inlets. Takes a while to set; dig in gently.
Weed and seagrass	Poor	The anchor skates over it, or pulls out a clump and drags. In the Mediterranean it is usually Posidonia.
Rock	Poor	Nothing to dig into; the anchor may also jam under a ledge.
Coral	Never	Easily destroyed and protected wherever it grows. Use a mooring or anchor on sand well clear.

Posidonia is a seagrass found only in the Mediterranean. It grows in dark green meadows a few metres to forty metres down, shelters fish, keeps the water clear and holds the sand of the beaches in place. A single anchor and chain dragged through it tears out growth that takes decades to come back, so it is protected across the region.

Look down before you drop: light sand is good, dark patches are seagrass or rock. In clear Mediterranean water you can see the bottom in ten metres.

Scope: how much chain

The scope is the length of chain you let out, compared with the depth. The anchor holds because the pull on it is along the seabed: enough chain lies on the bottom that the boat pulls the anchor flat, not upwards. Too little chain and the boat lifts the anchor out every time it snatches in a gust.

chain = (depth + bow + tide) × 4 to 5

Measure the depth from the bow roller, not the waterline, and add any tide still to rise. Use more if it blows.

Conditions	Rule of thumb (all chain)
Settled	Light winds and a good forecast: four times the depth is the least to use.
A breeze expected	A sea breeze or a fresh night forecast: five times the depth.
Strong wind	Strong wind or gusts off the hills: seven times or more, if the swinging room allows.

These are rules of thumb for chain. If part of the cable is rope, use more. In most of the Mediterranean the tide is a few tens of centimetres and you can ignore it; in Phang Nga Bay the range is up to about three metres at springs, so use the depth at high water.

Worked example

A bay on Šolta, with the afternoon breeze expected

1The sounder shows 7 m. The bow roller is about 1 m above the water: 7 + 1 = 8 m.
2A breeze is due this afternoon, so five times: 5 × 8 = 40 m. The chain is marked every 10 m, so let out 40 m, to the fourth mark.
3Swinging room: 40 m of chain plus 12 m of boat is about 52 m in every direction.

40 m of chain, and a clear circle about 52 m in radius.

InteractiveScope calculator

Set the depth, the bow height, the tide and tonight's forecast. Try a deep bay with only 50 m on board.

Depth on the sounder: 8 m

Height of the bow roller: 1 m

Tide still to rise: 0 m

The forecast for tonight

Chain on board

8 m depth + 1 m bow = 9 m. 5 × 9 = 45 m, so let out 45 m (rounded up to the next mark).

Swinging circle: about 57 m radius (45 m of chain + 12 m of boat). A sea breeze or a fresh night forecast: five times the depth.

Dropping and setting the anchor

Brief the crew. One person on the bow with the windlass remote, one on the helm. Agree hand signals for “go ahead”, “stop”, “go astern” and “chain out”, because the helm cannot hear the bow over the engine.
Approach slowly, head to wind, or the way the boats already anchored are lying. Stop the boat over the spot you chose.
Lower the anchor to the seabed, then pay out chain as the boat drifts back or goes gently astern, so the chain lies in a line along the bottom. Never dump it all in a heap on top of the anchor.
Let it bite. At about three times the depth, stop the chain and let the boat's weight pull it taut. The bow swings to face the anchor.
Full scope, then dig in. Let out the rest, then go astern, gently at first and then firmly, for a minute. Watch a transit abeam (below): if it stays still, the anchor is set.
Snubber on. A rope bridle hooked onto the chain takes the snatching load off the windlass and quietens the night.

By day, an anchored boat should show a black ball in the rigging; at night, an all-round white anchor light. Charter boats have the light; ask where the ball is kept. When you leave, motor gently up towards the anchor while the bow takes in the chain: the windlass lifts the anchor, it does not pull the boat.

Is it holding? Transits, the plotter and the alarm

A transit is two objects ashore, one behind the other: a chapel on the hill and a rock on the shore, a tree and a headland. Pick one abeam (to one side of the boat) as soon as the anchor is down. While it stays in line you are not moving. If it opens steadily, you are dragging. Expect a little movement as the boat swings; take a second transit ahead or astern to be sure.

The plotter track. Zoom in after an hour. A boat swinging on its anchor draws neat arcs; a dragging boat draws a line downwind.
Anchor alarm. Most plotters and many phone apps have one. Set its centre where the anchor went down (most apps let you mark it, or move the centre ahead of the boat by the chain length), with a radius a little bigger than your swinging circle.
Anchor watch. If the wind gets up in the night, someone gets up too: check the transit, the alarm and the boats around you.

Swinging room

A boat on its anchor swings round it as the wind changes, so it needs a circle of clear water with a radius of about the chain plus the length of the boat. Boats nearby swing too, and usually together, so overlapping circles are normal in a busy bay. What matters is that you lie as your neighbours lie, with similar scope, and that you are not on top of their anchor or chain. The first boat in has the spot: give them room, and if you anchor too close, it is you who moves.

InteractiveDrop the anchor in the practice cove

The cove is fictional, open to the south, with no tide. Tap to drop your anchor, choose the scope and the wind, and see what your swinging circle reaches. Arrow keys move the anchor.

Scope

Wind from

Tap the cove where you would drop the anchor. You are a 12-metre yacht drawing 2 metres.

More chain holds better but needs more room. Choose the spot for the scope you will need tonight, not the one you need now.

Lines ashore

In narrow coves there is no room to swing, so boats anchor with a line ashore. It is the normal way to spend a night in the Göcek bays, in many coves in Croatia, and in inlets such as Kioni in the Ionian.

Drop the anchor well out in the deeper water, then reverse slowly towards the shore, letting out chain.
A crew member takes the end of a long floating line ashore by dinghy, or swims it, and passes it round a rock, a tree (with chafe protection) or a ring set in the rock. Some bays, especially in Turkey, have rings or bollards for this.
Bring the end back to the boat, so you can let go from on board without anyone going ashore.
Take in the slack on the line and tighten the chain, so the boat sits between the anchor and the shore and cannot swing.

With the boat held still, a wind on the beam puts a big sideways load on the anchor, so a line ashore suits a cove sheltered from every likely wind. Stern-to on a town quay, the Med mooring, works much the same way with the quay instead of the tree: Lesson 8 covers coming into a berth.

Mooring buoys

More and more bays have mooring buoys, laid to protect the seabed or simply to fit more boats in. Where they exist, anchoring is often not allowed.

Where	What to expect
Croatia	Paid buoy fields in many popular bays. A boat comes round in the evening to collect the fee. Some konobas (family restaurants) have buoys for their guests.
British Virgin Islands	Paid mooring balls for the night in almost every bay. National Parks moorings at sites such as the Baths and the Indians are for day use only, with a time limit, and every boat needs a National Parks permit.
Cabrera, Mallorca	A national park: book the navigation permit and the buoy online in advance; anchoring is not allowed.
Aeolian Islands	Paid buoys in many bays, including Panarea and Stromboli, with the fee collected by boat.
Phang Nga Bay	National park moorings at some islands to protect the coral. Check one suits a boat your size.

Picking up a buoy

Have a long mooring line ready on the bow, led through the fairlead and back to a cleat, and the boat hook out.
Approach slowly into the wind, or the way the moored boats are lying (they show the combined effect of wind and current).
The crew on the bow points at the buoy all the way in, because the helm loses sight of it under the bow in the last few metres.
Pick up the buoy's pick-up line or ring with the boat hook. Pass your own line through the loop and back to the same side's cleat, or rig a bridle to both bow cleats. Don't rely on a short pennant dropped over a cleat.
Check the buoy looks sound and is meant for a boat your size, and never use a private buoy without asking.

Key terms

Scope: The length of chain let out, as a multiple of the depth from the bow roller: four to five times in settled weather, more if it blows.
Holding: How well the seabed grips the anchor. Sand and mud are good; weed, rock and coral are poor or off limits.
Posidonia: A protected Mediterranean seagrass growing in dark meadows. Poor holding; anchoring on it is banned in some areas.
Swinging circle: The clear water a boat at anchor needs: a radius of about the chain plus the boat's length.
Transit: Two objects in line, one behind the other. A transit abeam that stays in line shows the anchor is holding.
Anchor alarm: A plotter or phone alarm that sounds if the boat leaves a circle centred on the anchor.
Snubber: A rope bridle hooked onto the chain to take the load off the windlass.
Windlass: The electric winch on the bow that raises and lowers the anchor chain.
Line ashore: A long line from the stern to a rock, tree or ring, holding a boat at anchor in a narrow cove so it cannot swing.
Mooring buoy: A buoy fixed to the seabed for boats to tie to, often paid, sometimes for day use only.

Exercises

Check your understanding. You get a second try at each question, then the worked answer. Score 70% or more to complete the lesson; your progress is saved in this browser.

Which seabed gives the best holding for a charter yacht's anchor?

You can see dark meadows of Posidonia seagrass under the boat, with lighter patches between them. What do you do?

A northerly is forecast all night. Where would you drop the anchor? (Your boat is 12 m long, draws 2 m and will use about 40 m of chain.)

The sounder shows 6 m, the bow roller is 1 m above the water, and the night is settled. At five times the depth, how much chain do you let out?

In 4 m of water, with a 1 m bow and a strong wind forecast, you use seven times the depth. How much chain is that?

You have 35 m of chain out on a 12 m yacht. Roughly what radius of clear water do you need around the anchor?

After anchoring you line up a chapel on the hill behind a rock on the shore, abeam. Ten minutes later the chapel has moved well to the left of the rock. What is happening?

Where should the centre of an anchor alarm's circle be?

On the practice chart, tap the Kerran Roads anchorage.

A fresh northerly is forecast tonight. Is Kerran Roads a good place to spend the night?

Taking a line ashore round a tree, why bring the end back to the boat?

How do you approach a mooring buoy?

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Scope and swinging room

Fresh numbers every time: how much chain, and how much room you need.