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.
Mammals have a horizontal tail.
Fishes have a vertical fin.
Turtles are in economy mode when they are sleeping. If they are woken during night, they may not have enough air to return to surface.
So, please be careful during night dives!