bouncy ??

Canoes etc can have flotation bladders. Ping pong balls would probably also work if the floor was nailed down or it could be a big candy dish
 
Seen some threads on using those for buoyancy on the world sea fishing boat forum, there is a thought you should put them in bags as a small breach could let them out.
 
It replaces the foam (flotation) after it becomes waterlogged and rotten after a few years and aids draining. A much better solution imo
 
Seen some threads on using those for buoyancy on the world sea fishing boat forum, there is a thought you should put them in bags as a small breach could let them out.

If you did get holed, at least CG could follow the colourful trail to find you :D
 
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