Getting the treasure is easy; escaping is the challenge.
Let's be honest: the only real threat to the one who bears the treasure is not the skeletons (who can easily be outsmarted by anyone who is not afraid of some fall damage) but other players (and sharks).
Sure players can avoid carrying loot in the waters and sharks but in return the players will have to try to shoot the treasure onto the boat (or try to fish it out of the water if their aim was off - which have sharks).
I'd say skulls should be passable to be fired in a single shot but treasure chests should be divided into smaller sacks which can be loaded into the cannon.
