A simple solution to providing a shower if you are skiing etc and want to wash off the salt water if you are staying out on the boat for the day.
Basically camping showers. Its a plastic bag you fill with water that has a tube and shower head on the bottom of it. The bag will warm in the sun but could be put in a jockey seat then pulled out and hung on the A frame as it is gravity fed.
May or may not be the solution you are looking for but cheap. £8