I think his dad was, you know...lonely and uh...decided to bang a shark??? you know "palma" dont satisfy you after a while...some bang goats,...he banged a shark...its only normal xd:flaw:
Yeah, there's probably a clan of shark people or somethingRemember that in manga 507, this big fat dude had Shark Skin and he looked like a bald, fat virzion of kisame. maybe he's in some clan that look like sharks. Also it could be from useing samehada.