Play with a boat.

The crew minus one person pulls the boat whilst swimming.

The other person stands on the quarter-deck with his/her heels against the stern, so that he or she will be able to fall overboard and not in the boat.

He/she holds an oar with its end protected.

The boats sail close to each other and the knights try to push their opponents off their boat, just like knights used to push each other off their horses in a medieval tournement.