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What to do if you are taking on water and potentially sinking

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What is the issue?
Boats sink for a number of reasons. Overwhelmed by weather, faulty through hull fitting, lack of maintenance, collision or grounding strikes. A small holing may appear trivial but a five cm hole below the water line will leak three hundred litres per minute. A 10cm hole at the same depth will leak one 1,100 litres per minute. Enough to sink a 30ft yacht in 12 minutes. It’s your worst nightmare, you are bringing aboard tons of green water. You are taking on water faster than the pumps can evacuate it. What do you do now?

Why address this?
Depending on the size and location of the hole, if you are quick thinking and act fast, you can almost certainly save your boat and could even arrive in a safe haven with her bailed dry ready for repair.

How to address this?
Boats rarely sink, but as the old saying goes ‘stranger things have happened at sea.. The priority is always to avoid placing a vessel in a position that could lead to a sinking and having it well maintained so that failures that precipitate one are avoided. But no matter how diligent you are and how well maintained a vessel is, accidents do happen and situations can get out of control quickly. Then be prepared for events that could sink the vessel and having a plan of action thought out in advance will help to minimise the potential of losing the vessel.


You can greatly reduce the chances of your boat sinking due to wear, tear, and corrosion by adhering to a regular maintenance schedule:

  • • Check for any cracking in the hull.

  • • Inspect your sterndrive gland or bellows annually.

  • • Check your stuffing box every time you visit the boat. Stuffing boxes are one of the few thru-hull fittings designed to allow some water into the boat, at least when the motor's in use. But this can get out of hand. Adjust it so that there are no leaks when engine off and about 2-3 drops per minute when the shaft is turning. Repack the stuffing seasonally.

  • • Replace your impeller every second service.

  • • Systematically check all the vessel's hull penetration fittings such as plumbing seacocks, log and echo sounder transducers, engine inlets & outlets, propeller shaft etc.

  • • Make certain that all of the fittings are marine-grade parts and in good condition. Cocks are only rated for five years so if there is any concern regarding a seacock, or there is some indications of fatigue or corrosion, replace it immediately with proper DZR or bronze.

  • • If you see dampness around a transducer, use epoxy temporarily fix it. Unfortunately, water may have intruded into the hull itself, resulting in saturation or de-lamination. It is advisable to haul the boat and deal with the leak as soon as possible.

  • • Check that all hoses are properly connected, double clamped with stainless steel hose clips and that all hoses are in good condition. Don’t overlook your engine raw-water hose. Make certain it has a swan neck fitted Experience and take early corrective action at the first signs of wear or degradation.

  • • Check that cockpit drain pipes are in good order, functioning and inspect all the plumbing to make sure water cannot drain into the boat.

  • • Confirm that the bilge pump is fully operational and installed at the lowest part of the bilge so it can detect the water level and automatically activate when needed. Add LED(s) warning lights to visually indicate its operation Experience should it be trying to deal with an unoticed inflood because its sound was masked by engine noise.

It is advisable to incorporate this checklist into your pre-departure schedule. Likewise, make sure to do a similar inspection and shut off of all the cocks as part of a post-trip routine, about 70% of sinking’s occur to boats whilst alongside.


Preparing for a sinking situation, with the right tools and materials and knowing what to do with them is vital. When you first see the green water rising below deck and the surge of adrenalin hits, nothing will help you more to stop that turn into an outright panic than knowing you have tools and resources to deal with the situation.

  • Wooden plugs or bungs: All vessels should have ample wooden bungs or plugs that can be used to stop leaks. They offer a simple, inexpensive and effective solution to a potentially disastrous problem. Just be aware that wooden plugs cannot be expected to make a watertight fit, but even putting a single plug in a hole should reduce the flooding to a leak that should allow an electric bilge pump to gain ground on the flooding. Plugs will always work best if you wrap a rag around them before insertion. The cloth tends to keep the plug in place and fills some of the gaps between the plug and the edges of the hole.

    Wooden bungs are so inexpensive that each through-hull fitting should have an appropriately sized plug tied off to fittings and ready to deploy. Check the condition of the plugs when inspecting the seacocks as they can swell or split if left in damp conditions for long periods. A central reserve of additional wooden bungs and some hi-tech form-fitting emergency plugs should be stored in a convenient dry locker.

  • Forespar’s Sta-Plug bungs
    Image: Michael Harpur
  • Hi-tech form-fitting emergency plugs: In addition to the softwood bungs it is important to have some hi-tech form-fitting emergency plugs, such as Forespar’s Sta-Plug bungs. Although much more expensive than wooded plugs the hi-tech bungs are able to conform to the shape of the hole enabling it to more fully seal around the edges and hold the plug more securely in place. They may thereby be used to fill irregular shapes of hull impact breaches are more reliable in through-hull failures.

  • Mouldable polymer: A play-doh like product called 'Stay Afloat' is a simple and versatile material intended to be used as an instant leak plug and sealant to stop or slow water leaks in boats. Used as is it requires no mixing, measuring or curing and is easily moulded and applied, by hand, into any shape that the hole happens to be.

  • 2-3 mm plywood boards, some aluminium and plastic: Carry 4 or 5 pieces of 3mm plywood cut in several sizes, like 30 cm square. Strips of aluminium or plastic are also useful. You can make these yourself to whatever size you think are appropriate and have them ready for an emergency. Carry a saw and hacksaw will enable you to tailor them to fit up against bulkheads.

  • Carpenter's brace: Have a carpenter’s brace Experience aboard, appropriate bits and self-tapping screws. Attempting to hammer nails into fibreglass is futile nor will self-tapping screws bite in of their own accord. Pilot holes have to be pre-drilled into the fibreglass and, in these conditions, an electric or battery-operated drill cannot be relied upon as the tools will be immersed in water a great deal of the time.

  • Carpenters Brace with a reversible ratchet
    Image: Courtesy of Faithfull

  • Epoxy emergency repair kit: Have an underwater repair kit with a two-pack epoxy bonding system promising rapid cure aboard. An emergency repair kit more elegant short-term repairs can be made if necessary. There are several emergency hull repair kits available on the market to help affect a semi-permanent repair. Epoxy kits like these are not your first line of defence. They are used after the flooding is stopped, the boat is bailed, and you need a more permanent patch to get you to your safe haven.

  • Hull collision mat: Make up a three-metre square hull collision matt Experience from a waterproof tarpaulin with eyelets and solid double stitched cringles prepared for this purpose. This may be used as a temporary external ‘patch' that can be positioned over a hole.

Hull collision matt
Image: Tony Gibson

  • Create a watertight compartment: Making arrangements to bolt in place a bulkhead 'damn board' Experience made of marine plywood, up to about ¾ of the way up the passageway into the front of the boat, can create a watertight compartments in the event of a collision.

Judge what repair material you want to carry by how far you venture from help. The benefit of all of these tools is that the brace, self-tappers, and the epoxy kit, collision mat is that they may be used for a variety of repairs and other purposes aboard. All of which is good for the emergency moment, as out of sight generally means out of mind.

Finally, keep an emergency grab bag and additional waterproof bags, to help protect additional supplies, so if the boat is sinking you don’t have to abandon resources as well as the boat. Ideally, you’ll want to keep in here a mobile phone, handheld radio, first aid kit, fresh water, food rations, warm clothes, a knife, torch and a couple of flares.


The chances are you will know that you have collided with something. There will be the bump and deceleration from the object, the crash of a mighty wave or the ominous scraping of rocks. The hole needs to be staunched very quickly or the vessel is lost but the advisable order of priority is as follows:

  • Stop: If sailing heave-to immediately, as the damage is likely to be on the leeward side. If you are motoring, trim the boat as then the chances are the damage will be on the forward part of the boat near the waterline.

  • People safety first: Assuming there is two or more aboard and uninjured get everybody to put on life jackets. Assign someone to make the life raft ready and to prepare the grab bag. But do not launch the life raft yet, you only get into the life raft if you can step up into it – i.e. the boat is actually sinking beneath you which is one of the key lessons of the 'Fastnet 79' disaster (link to download a zipped PDF of the special incident report External link).

It is best to notify the Coastguard early just in case the situation escalates
Image: US Coastguard

  • Contact the Coastguard: Notify the Coastguard of the situation via the ship's VHF Experience. Let them know your exact location, that the boat is taking on water and your initial visual assessment. It’s important to do this first should the water level rise enough to short-out the batteries. You can call back later if you resolve the situation but it is important to make them aware of the problem even if you have a hand-held VHF radio for the worst case, its range will be much less than that of the yacht's.

  • Bail and buy time: Get your bilge pump working and the crew working any backup manual pumps to help remove the in-flood. If you have enough hands aboard pull up the sole boards and assign people to start bailing directly into the galley sink, or the cockpit if you have an open transom. A last line of defence is to shut off the engine's seawater intake valve and disconnect the hose. Then drop the end of the intake pipe into the bilge water and use the engine as an emergency pump. As the water level drops, ease the throttle so the engine doesn't overheat and reconnect. This solution can be formalised by adding a 'Safety Seacock Converter' Experience to the boat.

  • Find the hole: Now you need to find whatever is causing the leak. Pull up the sole boards in the main fore-and-aft passage to expose the length of the bilge and check and empty the lockers until you find the hole.

  • Damage control: Once it is found jam whatever you have to hand over the opening to staunch the gap: towels, cushions, clothing or even a sail, anything that could slow the sinking down. A pillow or a cushion held in place by hand or foot can greatly reduce the flow of water. If you can brace the pillow in place this will provide you with the ability to start working on a better solution. Don't worry about the first solution holding, you are still buying time at this stage so you can properly assess the situation and plan a better repair later.

  • Externally patch If you can’t get at the hole from below decks try to get a collision mat, or if you have not got one a sail, and place it over the hull externally. You will have no choice but to get this right, and it is possible.

  • A more durable repair: Once you have the flooding under control, and you're on top of the water ingress then, you have time to think about the wider situation. Can you make way to a safe haven with the current set-up or do you need to rig a more solid repair?

    If you can make it with what you have already put in place simply secure it. If not this is the time to get the brace out and start screwing plywood boards on and/or use emergency epoxy solutions. Remember these repairs don't have to be pretty, they just have to stop the water, or at least reduce the flow rate until you get the boat out of the water.

    It is always advisable to avoid a repair that involves a crew member going into the water because it's too easy to drop tools and it's just asking for a compounding problem. But if the situation lends itself a bolt through the middle of a strongback on the outside of the hull passed through to a section of timber inside will provide a highly durable solution. Particularly so if a rubber matt is used to helping create a tight seal. This will only work if it is safe to go over the side of the boat. It is a solution best called upon when conditions lend themselves to it, the boat is not in jeopardy and you can make a plan that has prioritises the safety of the person going over the side. It cannot be carried out in the heat of the moment.

    If its too rough or dangerous a way to still plug a leak from the outside, without having to go over the side, is to push something that will float out through the hole with a line attached. Then grab the floating object, or use a boat hook to snag it. With the line in hand, you can pull back in from the outside, or through the hole, whatever is needed. It is essential that someone is doing whatever it takes to staunch the in-flood while things are being put together and quickly passed through.

    Holes above the waterline should not be overlooked, they may not appear immediately dangerous, but as the boat rolls or settles, they could become submerged and provide a new source of in flooding.

  • Keep an eye on it: Once you get the boat moving again, check your temporary repair regularly. Have everything you need ready to hand in case the patch fails and you have to do it all over again. Most temporary fixes will hold at sailboat speeds. With the extra drag from your patch, you won't be going very fast anyway.

  • Haul out as soon as possible: Regardless of how far offshore you are, start heading back to land. Go to the nearest safe haven that can handle your vessel and haul out or dry out alongside and attend to a more durable repair as soon as possible.

If all attempts to staunch the flow fail and shallow water is close at hand, head inshore and consider the option of intentionally grounding your boat. Grounding your vessel is far better than losing it, even if you do incur a little damage in the process. Try and find a safe spot, without sharp rocks or fierce waves that could make things worse.

Most boats tend to float so stay with it if it is safe to do so
Image: US Coastguard

If, however, the boat sinks completely, it's time to get off. But, if it's safe to do so, don't leave without taking as many supplies as possible. If it’s safe, stay with your boat. You’ll have a higher chance of drawing attention to the situation and attracting help. Most boats will float even when capsized so don’t assume all is lost.


But you are not taking on water. If your engine has stalled, check for damage to the stern drive or shaft seal before attempting to restart it. If there is any damage, call for assistance. If you can restart the engine, start slowly heading back to land checking bilge periodically. If all is well, work your way back to your home berth and ask the marina to keep a watch on the vessel. If there is any sign of water intrusion, haul out as soon as possible.


If you're sinking and it has not been caused by a collision or a crashing wave opening up a crack, there is most likely a leak. Again, when you first see the sole boards floating and the cabin awash, heave-to and follow all the steps listed above to the ‘finding the hole’. Then as follows:

  • Has a water tank burst: Check that the water is salty and that it has not caused by a large freshwater tank failure so this may be eliminated.

  • Check the through-hull fittings: Systematically check through all the below-waterline hull penetrations, seacocks, log and echo sounder transducer fittings, engine inlets & outlets, propeller shaft hoses and hose clamps inside the boat. Ideally starting with the largest first. Some may be difficult to reach but you have to get to them all until you find the source.

    • ☐ Seacocks: Pay particular attention to the vessel's seacock as these are the usual source of this problem. Degraded seacocks normally fail as follows:

      • (i) The ball valve breaks when someone is operating it or knocked it accidentally. This would be the best situation as the source of the problem will be detected immediately.

      • (ii) A corroded pipe shears off at the hull, leaving nothing more than a hole through the hull.

      • (iii) The ball valve breaks off leaving just the through-hull fitting.

      • (iv) The hose degrades and/or comes off the tailpipe above the ball valve.

    • ☐ Transducers and sensors: Log and echo sounder transducers and sensors fittings can fail too. These penetrate the hull well below the waterline, and unlike most below waterline fittings, they do not have a seacock. Any sort of a failure in these will bring water into the boat.

    • ☐ Propeller shaft: Check that the normal one to two drips a second has not turned into a stream. Adjust the stuffing box so that there are no leaks. Check that it is still there and has not pulled free out of the boat leaving a through-hole. Any sudden loss of power in reverse will precede this but propeller shafts often come free of its mount and fall out.

    • ☐ Check the engine exhaust hose: If you have been motoring and the impeller gave way the engine will overheat and its hot gases can melt the engines raw-water hose. This opens the closed loop and allows water to enter the boat.

  • Stopping the flow: When the culprit is found your immediate reaction will be to cover the aperture with your hand which will help. Hopefully, a bung will have been positioned close to hand that can be substituted quickly or a crew member can run and find one. Failing that, jam whatever you have to hand over the opening to staunch the gap, as above.

Then follow the above guidelines. Generally, a through-hull fitting can be safely secured with a bung, made snug by rags, and particularly so a hi-tech form-fitting emergency plug, so the situation is less critical.

With thanks to:
Michael Harpur, Yacht Obsession
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