The (weak/strong) attraction of one water molecule to another through those slight charges is called biology 1

substitution is the answer in this case

fumikage isn't really a bird, and tsuyu does have teeth. tsuyu has a transformation quirk which still allows her to be partially human. otherwise we'd have a large frog running around. fumikage has teeth because again, he isn't a bird. his head was a quirk mixture if i'm correct.