abs or pvc pipe can make a nice raft too.
hemp fiber matting makes good option to build with suposedly 300x stronger than wood.
other fun ideas
make an unsinkable boat for animals to tread around on. could steer with their heads or a couple pedals and electric motors depending on what their skills are. could even scale it up for cows and horses to be extra funny.
https://www.thingiverse.com/thing:4582461 new buoyancy engine for boats