We can hear the bull shark is very dangerous because of attacks near La Réunion island.
However, tens of them are living at 600 feet from the famous beach of Playa Del Carmen in Mexico. And there are no attacks.
Some sharks can stay motionless on the sand (white tips reef sharks, nurse sharks, etc.).
These sharks don't have to swim to bring oxygen to their gills like other sharks (grey, hammerheads tc.)
Mammals have a horizontal tail.
Fishes have a vertical fin.
