Prosthetics (or artificial limbs) vary enormously in their design and capability. Most don’t like sea water! This is due to the corrosive action on metals. Most prosthetics are built from a variety of different metals. These are subjected to electrolysis (or cathodic action) which degrades the least noble metal first. It’s the same principles that operate in batteries but it’s destructive in this case.
So you need a suitable prosthetic leg. If you’re an NHS patient you can usually obtain a “beach limb” which will be suitable for sea kayaking. It may not have all the functionality of your walking limb but is likely to be good enough.
For below-knee amputees it’s all pretty simple. You probably will keep the prosthesis on all the time, as having control of a natural knee will mean you’ll be as mobile as any other person. Put foam padding around the prosthesis to protect clothing, kayaks and other people.
For above-knee amputees, if you become a committed paddler who wants to enjoy greater mobility and the benefit of sea-water tolerant prosthetics, take a look at the OttoBock Aqua-Knee 3WR95. It’s an excellent knee unit, is very robust and has a high degree of functionality. It’s even quite good for cycling due to it’s great deflection range. Also consider the Aulie 802/902 knee, which offers solid and reliable performance. The Otto-Bock Genium X3 is the gold standard in micro-processor knee systems. It is rated IP-68, capable of being immersed in sea water to a depth of 3 metres for up to 60 minutes. I have one and have been testing it extensively. On land it is peerless.
Reliable suspension in a wet and cold environment can be tricky. Getting a silicone liner into a wet socket is usually easy. However, it can also release unexpectedly. This can be dangerous if you’re carrying a sea kayak or on slippery surfaces. I use an Iceross Seal-In X5 TF as I find it gives sufficient stump protection, keeps me warm enough (even in the water) and I like the backup of five individual seals. If it gets torn it will still do the job and durability is good. If like me, you rely on a suction socket then it’s worth considering a back-up/alternative/auxiliary suspension method such as a neoprene belt. It will prevent your prosthesis from coming off unexpectedly. Ask your prosthetist for advice here.
Getting your waterproof prosthesis to fit correctly in the cockpit of your sea kayak is important. It’s crucial that the angle allows you to use it comfortably as a thigh brace. Your prosthetic foot might be too long to go where it needs to go. If the foot prevents you from getting the angle right, consider chopping the “toes” off. They are probably only rubber and it is unlikely to affect your ability to walk. Important note – don’t do this if it’s also your main walking prosthesis. Always consult your prosthetist first.
A waterproof prosthesis tends to have either a fixed or quite stiff angle joint. This makes walking difficult on slippery surfaces, especially weed-covered concrete and rock. Be extremely vigilant and avoid them if possible. When there is no choice, you might find getting down onto your backside is the best option. You can’t fall any further than this. If you’ve got company, ask for help and don’t feel guilty about it.