Once in a while when you look down at water you have strobe effect blue lights that are at the bottom of the screen.
If you are inside your house a sarco is able to kill you through the wall/floor depending on what level you are on. I.e. Standing on a balcony sarco is under you=dead/hurt.
Dino's are able to go semi through walls like a brontosaurus tail or a carno head.
These both happen without the walls being damaged or broken.