There is a particular sound a flooding boat makes that you never forget. Not a gush, but a steady busy gurgle from somewhere you cannot see, and a sole that flexes slightly under your feet because there is water above the floorboards. The first time I heard it, mid-Channel on a friend's boat, the cabin smelled of diesel and panic and we wasted ninety seconds doing nothing useful because none of us could find where it was coming from. We found it. We were lucky. The numbers explain why luck mattered.
A flooding boat is a race between the water coming in and the water you can get out, and the brutal arithmetic is that you will probably lose the pumping race if the hole is real. A 25-millimetre hole one metre below the waterline lets in over 150 litres a minute, around 9,000 litres an hour. Few cruising boats carry a pump that can move that, so the whole game is to find the source and stop it, not to out-pump it. Everything below flows from that one fact.
Pump capacity: know the truth before you need it
Marine safety guidance puts the minimum rating for an emergency pump at 200 litres a minute, and even a serious high-capacity electric pump rated around 3,500 gallons an hour, roughly 220 litres a minute on paper, delivers far less in reality. Real-world output is often about 60 percent of the rated figure once you account for discharge height, hose length and a clogged strainer. So a pump that says 220 on the box might move 130 litres a minute on a bad day, which a single substantial hull breach can beat on its own.
The lesson is not to despair of pumps. It is to size your expectations: pumps buy time, they do not win against a hole. Time is exactly what you need to find and plug the leak, get to safety, or let rescue reach you. A high-capacity pump can keep a holed boat afloat for hours, and hours can be everything.
Find it fast
You cannot stop what you cannot find, and water on the move is hard to trace because it runs aft, hides under sole boards and sprays off the hull. Work fast and systematically.
- Taste or smell. Salt means it is coming from outside; fresh and clean might be a burst water tank, which is not an emergency.
- Check the through-hulls first. Every skin fitting is a candidate: the log, the depth transducer, the engine raw-water intake, the heads inlet and outlet, the cockpit drains. A failed hose clip or a split hose at a through-hull is a common source and a relatively easy fix.
- Check the stern gland and the rudder stock, both classic culprits.
- Lift the sole and look for the level rising, then watch where the inflow is strongest. A torch and a hand in the bilge will often find the stream before your eyes do.
If you genuinely cannot find it and the level is rising, treat the worst case and prepare to abandon to the liferaft while you keep working, but do not stop searching. Most leaks are found.
Slow the flood
Once you know where it is, the priority is to stem the flow, because every litre you stop is a litre you do not have to pump. Carry the kit that makes this possible and know where it lives.
- Soft tapered plugs. A set of conical softwood or foam bungs, sized to your skin fittings and ideally tied to each one, will hammer into a failed through-hull or a snapped seacock. This is the single highest-value piece of damage-control gear on the boat and it costs very little.
- Emergency sealant putty. A tub of marine emergency putty moulds over an awkward leak, around a deformed fitting or a small crack, and buys time even underwater.
- Improvised bungs and stuffing. A wooden plug wrapped in cloth, a wine cork, even a fender forced against a hole from inside and braced, all have stopped boats sinking.
- For a larger breach, a collision mat dragged over the outside of the hull and held by the water pressure can cut the inflow dramatically while you pump and run for port.
Close the seacock if the leak is downstream of one. It sounds obvious, and in the heat of the moment people forget the simplest fix is often a quarter-turn away.
Pump everything you have
While one person stems the leak, another pumps. Run the electric bilge pump, work the manual pump, and remember the biggest pump on most boats is the engine: a hose from the raw-water intake into the bilge, with the seacock to the sea-strainer closed, turns the engine into a powerful emergency pump. A bucket in a chain remains startlingly effective; a determined crew with two buckets can shift a great deal of water. Keep at it. The aim is to hold the level steady long enough for the plug to work or for help to arrive.
Assign the jobs before chaos assigns them
A flooding boat goes wrong fastest when three people try to do the same thing and nobody does the others. In the first calm seconds, the skipper should split the work out loud: one person finds and stems the leak, one person pumps and bails, one person handles navigation and the radio call. On a shorthanded boat one of you does two jobs, but the principle holds, name the tasks so that searching, stemming, pumping and calling all happen at once rather than in a panicked queue.
Brief the crew on where the damage-control kit lives before you ever leave the dock, because a person hunting through a flooding cabin for the bung bag is a person not stopping water. The tapered plugs, the putty, the soft-wood bungs and the heavy gloves should be in one grab bag in a known locker, not scattered. Keep the manual bilge pump handle clipped where you can reach it without thinking, and make sure at least two people aboard know how to rig the engine raw-water intake as an emergency pump.
Call for help early, not late
Do not let pride run the bilge dry of options. If the inflow is winning, or you simply are not sure you can hold it, get on VHF channel 16 to CROSS while you still have power, a position and a working radio. A boat that is flooding but under control is a Pan-Pan; a boat you are losing is a Mayday. Our guide to the French distress and safety call procedure gives the exact wording and the useful French phrases, and it is worth reading before you need it rather than during.
Make the call before the batteries flood and die. The same discipline applies as in any French-waters emergency, from a rigging failure on a French passage to being caught on a lee shore: a controlled situation reported early gives the rescuers options. Saving life is free in France under the 1979 SAR convention, while towing a boat that is afloat but disabled is a paid service, with the SNSM typically invoicing between 340 and 700 euros depending on the boat and the means. None of that should ever weigh against making the call when people are at risk.
Prevention is the cheapest pump
Most flooding emergencies start at a fitting that should have been checked. Soft, weeping or corroded seacocks, perished hoses, single hose clips where there should be two, a stern gland left to drip into a problem: these are the usual beginnings. A pre-season check of every skin fitting, hose and clip, and a tapered bung tied beside each seacock, prevents the great majority of these incidents. The same eye that finds these faults is the one our guide to used sailboat hull inspection trains you to use when buying.
We found that mid-Channel leak at a heads inlet hose that had finally given up at the clip. Thirty seconds with a screwdriver and a rag held it; a new hose at the next port fixed it. The water above the floorboards was a metre from a very bad day, and the difference was knowing where to look and having the cheap kit to deal with it. Carry the bungs. Check the fittings. Make the call early. The bilge does not negotiate.
