Used to do the Raft Race in the 8o's when it was a yearly event. One of our chaps went in the water because it was a very hot day.
Ended up having 2 weeks off work when he got an infection in his testicles...They swelled up like rugby balls..
Bloody good fun though... ;D
Make a raft an put a big painted cardboard (waterproof) cut out of a motorbike in the middle
When we did it we had a loch ness monster on ours