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Flooding-Fighting Aids

"Panic tends to rise with the water level but it’s important to remain thinking clearly ..."

First Response

Flooding as a result of a crash or a failing through-hull will demand immediate and concerted action of the complete crew. In this situation is very helpful if everyone on board is well aware of the elementary first steps to be organized:

  1. - start bailing the bilge (manual and electrical bilge pump)
    - check the location of the leak and the severity of the problem
    - if help can be expected to be within reach, send out an emergency call by radio
  2. - start preparations to deploy the life raft and to abandon the yacht
    - try to temporarily stop the leak and try to prevent taking too much water
  3. - find a more permanent leak-stopping solution that enables sailing home

A serious leak will have the sole boards awash in a few minutes. As time is crucial and tasks must be done in parallel, each crew member should know his precise role in this task list.

Flooding Countermeasures

This section will summarize some flooding-fighting measures that have been proven to work to a certain extent. Since each flooding scenario is different, it is worth to collect and absorb some different ideas to be able to come up with a practicable solution in a tangible case of emergency.

Wooden Bungs

sail052h_E.png This is a quick and easy to deploy solution if the leaking hole is perfectly round and not too wide. This is usually the case if failing sealocks or other through-hull mounted hardware are the problem. After the bung has been put into the hole it will swell in the water, forming a good seal. If the bung can be extra fixed to stay in position, this may be a practical more permanent leak-stopping solution.
Bugs are available in a variety of sizes at low cost. They must be kept in a dry place in order to maintain the required swelling capability for securing a good seal.


A Cushion, a pillow, a blanket or even a towel may be stuffed into a larger hole to temporarily reduce the intake of seawater. These things are readily available in different sizes on almost any yacht and they work reasonably for some time. An appropriate plywood board may be used to keep the cushion firmly pressed against the hull using your hands or feet. Wrapping the cushion in a stable plastic bag before stuffing it into the leakage hole, may improve the effectiveness of this method. However, this method is unlikely to work for a longer time, but at least it can be used to gain some time while trying to find a better way of sealing the hole.

Fothering, Leaksails or collision mats

sail052h_F.png In nautical context, "fothering" refers to covering a leak in a ship with a sail containing ropes to bring it in place at the outside of the hull and thus to prevent the ship from sinking after being damaged. This was the technique used to help to refloat Captain Cook's HMS Endeavour after she went aground on the Great Barrier Reef on 11 June 1770.
For this technique principally any available (spare) sail can be used. Fixing the sail at the outside of the hull has the advantage, that the water pressure will push the sail firmly into the hole. But it is not simple to bring the sail in the correct position and even synthetic sails are not very watertight. As an alternative a special "leaksail" also referred to as "collision mat" can be prepared as part of the emergency hardware. This would consist of triangular shaped "sail" made of a strong, watertight fabric and supplied with long ropes at each of the corners. The actual size will depend on the size and hull form of the yacht. Since this type of covering may also be (mis)used as sunroof, maybe even two or three differently sized "leaksails" can be stored on board.

More durable Sealing Solutions

The above ideas are primarily aiming at stopping the water from flowing uncontrolled into the boat. But the final goal is to establish a more permanent and durable solution that must enable the yacht to be sail-able again. Such a solution will depend on what is available on board to repair the hull and it will require a lot of improvisation to install a solid repair that allows to reach a safe harbour.

More lasting solutions may involve a combination of marine plywood, mats of fibreglass and some kind of epoxy repair kit. A piece of mat cut to size and glued in place with the epoxy and than secured with a board of plywood can seal quite effectively.

Here are some additional aids to build a durable sealing solution:

Stay Afloat Emergency Leak Sealant

Stay Afloat is a non-toxic, putty-like material that instantly plugs leaks in boat hulls and marine fittings by hand moulding into any shape. It will cling to wet or submerged substrates.
It can be used to seal broken through-hulls or hull punctures to instantly stop water ingress in emergency situations. But it can also be applied to stop any kind of small leakages on or below deck.

Stay Afloat works immediately with no cure time. This thick, wax-like consistency putty conforms and clings to any shape and substrate and may prevent flooding in an emergency. Its universal application is used extensively by emergency rescue personnel.

Self-fusing Silicon Tape

This is a non-adhesive silicone tape. The tape itself is not sticky. It is wrapped in an overlapping way and after applying pressure, the tape will melt by itself-which means that it does not need any messy adhesives that may leave any sticky residues.

It is applied as follows:
Remove the isolation film of tape, stretch the tape to twice of its original length and wrap it on the objects to be sealed. Always half-overlap it on previous wrap to produce a uniform buildup, until reaching the thickness you need. Apply final overwrap with zero stretch. After installation, press the tape so that it will self fused quickly. More layers should be applied for repairing pipe leakage with high pressure.

Through-Hull Failures

Beside getting damaged by a crash situation, there are also some "home-made" issues that may lead to unwanted holes in the hull.


Seacocks have three failure modes. The most common is where a corroded pipe shears off at the hull, leaving nothing more than a hole. The second is when the ball valve cracks, leaving just the through-hull fitting.
In the third failure scenario, the hose slips off the tail pipe inboard of the ball valve, or the corroded tail pipe disintegrates following a slight knock, while the ball valve is jammed and can’t be closed.

Log and Echo Sounder

Log and echo sounder transducer fittings can fail, too. Often the internal securing nut is mounted on a wooden pad. If it’s not installed properly, the wood can get wet and swell, shearing the nut off the thread, which means the fitting can fall out of the boat. If the fitting is on a sharp turn of the bilge, the outer flange isn’t supported across its full diameter and can crack. When the flange breaks, the internal fitting is fired into the boat by the water pressure. Another possibility is that the internal securing nut is overtightened, which can also lead to cracking and a similar result.
All manufacturers recommend the internal nut, once tightened, is covered with a fillet of epoxy or FRP paste that spreads onto the hull. Should the outer flange fail, the fillet will prevent the entire fitting from being pushed into the boat. However, this step is often omitted to allow for easier removal of the transducer for cleaning or replacement.


1. Yachting Monthly, "Major Leaks!", October 2011, pp 84-94.
2. Yachting Monthly, "Sinking!", September 2011, pp 32-40.

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