The first time I lost someone over the side on purpose was off the Glenan islands, flat calm, gin-clear water, and my teenage daughter went in before I had even cut the engine properly. She was fine. She was also, for about four seconds, drifting aft of the boat faster than she could swim, because there was half a knot of tide running that none of us had felt at anchor. That is the thing about swimming from a cruising boat: the water looks like a swimming pool and behaves like the sea.
I swim off the boat most days in season. It is one of the genuine joys of cruising the French coast, and it is also where casual habits get people hurt. What follows is how we do it now, after a few frights taught us better.
The two killers: temperature and the boat moving
Two things account for most swimming incidents from yachts, and neither is sharks or jellyfish.
The first is cold water shock. Anything below 15C is officially cold water, and immersion at or under that triggers an involuntary gasp, a spike in heart rate and blood pressure, and breathing you cannot control for the first few minutes. It can cause heart attacks in fit young people. In Brittany, where summer sea temperatures sit between 15C and 19C, you are right on that line in June and the shallow end of it even in August. On the Mediterranean it is a non-issue in high summer (the Cote d'Azur runs 22C to 26C in July and August), but jump into the Atlantic off the Brittany coast in early season and your body does not care that the sun is out.
The RNLI advice if cold water shock hits you is to fight the urge to thrash, roll onto your back, and float for 60 to 90 seconds until the gasp reflex passes and you regain control of your breathing. Drown-proofing yourself for a minute and a half is more useful than any swimming stroke in that moment. Hypothermia is the slower danger: in our latitudes it takes over 30 minutes of immersion in ordinary clothing before a person becomes hypothermic, so the cold that kills fast is the shock, not the chill.
The second killer is the boat. A yacht at anchor swings, sails, and surges on her chain. A boat lying to a mooring in a tide stream is effectively a fixed object in a moving river. Get downstream of it and you may not swim back. We never let anyone enter the water until the swim ladder is rigged, deployed, and someone has physically tested it can be reached from in the water, not from the deck.
Rig the ladder before anyone gets wet
I am dull about this and I will not apologise. The single most common way a strong swimmer drowns off a yacht is being unable to get back aboard. Topsides that look low from the deck are unclimbable from the water, especially tired, cold, and with a sea running.
Our rules, learned the hard way:
- The boarding ladder goes down before the first swimmer goes in, and the bottom rung must reach below the waterline. A ladder that stops at the surface is useless to an exhausted swimmer.
- One person stays aboard, dressed, not swimming. Always. They watch, they count heads, and they can start the engine or throw a line.
- A floating line streamed astern (a long warp with a fender on the end) gives a swimmer something to grab if the boat is sailing about on her anchor.
- Engine off and out of gear. A turning propeller and a swimmer are a coroner's inquest waiting to happen.
If you are swimming somewhere with any tide, get in at slack water and get out before the stream builds. On the Atlantic coast the tidal range does most of the deciding for you.
Where you swim matters
A marina is not a swimming pool, whatever the kids think. Stray current, fuel sheen, and the constant movement of boats under power make harbour swimming a poor idea, and many French ports prohibit it outright with a fine attached.
Anchorages are the place. The clear water of the Mediterranean calanques or a sandy-bottomed bay in south Brittany is exactly what you came for. But read the holding and the swing before you commit: if your anchor is doubtful, nobody swims, because the person aboard may need to drive the boat and you cannot do that with three people in the water around the prop.
Watch for moored buoys marking oyster beds and mussel lines on the Atlantic coast, and for the yellow swimming-zone buoys near beaches, which are a no-go for boats but a clue that swimmers and dinghies share the water there. Jet skis and fast ribs are the real menace near popular beach landings; fly your snorkel-down or dive flag and keep your group tight.
Kit that earns its place
You do not need much, but what you carry should be deliberate.
A swim ladder that genuinely reaches the water is non-negotiable. Beyond that, a couple of tow-floats (the dry-bag kind that doubles as a visibility marker) keep weaker swimmers buoyant and visible to passing craft. We keep a throw-line in the cockpit, the same one we would use for man overboard, because a swimmer being carried away by current is exactly that emergency in slow motion.
Footwear matters more than people expect. Sea urchins are everywhere on Mediterranean rock, and the spines snap off under the skin. A cheap pair of reef shoes saves a holiday. For early-season Atlantic swimming a shorty wetsuit changes the calculus entirely: it buys you time against the cold and turns a brief, breathless plunge into an actual swim.
Jellyfish, weever fish, and the other stingers
The French coast has its share of things that sting, and a little knowledge saves a ruined afternoon. On the Mediterranean, the mauve stinger (pelagia) blooms in warm summers and arrives in slicks driven by onshore wind; if you anchor downwind of a visible bloom you will swim through them. They are painful rather than dangerous for most people, but they will clear a boat of swimmers fast. A bottle of vinegar in the heads is the old cruiser's remedy for tentacle stings, not fresh water, which can make some species fire off more.
On the Atlantic side the hazard is underfoot. Weever fish bury in the sand in the shallows with venomous spines along the back, and standing on one as you wade ashore from the dinghy is agony. The treatment is heat: as hot as you can bear, for half an hour or more, because the venom breaks down with temperature. Reef shoes for wading and a flask of hot water aboard turn a medical drama into an inconvenience.
Sea urchins on Mediterranean rock are the most common injury we see. The spines snap off under the skin and work their way out over days. Tweezers, patience, and footwear are the whole answer.
Reading the anchorage before you let the kids loose
A swim should be a deliberate decision, not a reflex the moment the anchor bites. Before anyone goes in I look at three things. The depth under the swimmers, so I know there is water to swim in at the bottom of the tide as well as the top, because a bay that is two metres deep at high water can dry to nothing by low. The swing room, because a yacht that tacks about on her chain can put her counter over a swimmer's head. And the traffic, because a popular anchorage on an August afternoon is a thoroughfare of fast ribs and tenders that are not looking for heads in the water. We fly a flag, keep the group tight, and pick the quieter end of the bay.
A simple routine that keeps everyone aboard at the end
We brief it the same way every time, and it takes thirty seconds. Ladder down and tested. Engine off, out of gear. One person stays dressed and aboard, counting heads. Weak swimmers wear a float. Nobody swims upstream of the boat in a tide. And the moment anyone says they are cold or tired, they come out, no negotiation, because tired and cold is how a fun swim becomes a rescue.
Sea swimming off the boat is the best part of my cruising day. Treat the water with the respect the temperature and the tide demand, and it stays that way. If you also fancy putting a line over the side while you are at it, the rules are refreshingly simple, and I have written them up in the guide to a sea fishing licence for visitors. Get the swim safety right first, then enjoy the rest.
