How about Water = Death. Seriously, the hero can topple elder gods, destroy entire cities, eliminate entire crime syndicates by their self, and take fifteen shotgun shells to the face at point blank range but auto-magically be okay by finding a first aid kit in a bathroom, but homie can't swim? That kinda drives me nuts. I understand we need to have reasons why you can't fall off a platform, or set borders on levels, but really. Can't we come up with some other reason other than the savior-warrior-adventurer-god character never learned to doggy paddle?