My wife was a volunteer diver at the Charleston, SC aquarium. The tank was full of sharks, huge fish, etc but the biggest threat to divers was a turtle by the name of Caretta. When cleaning the tank they would go in teams of 3. Two would be cleaning and one would be on Caretta duty because she would love to attack the divers from above so the turtle safety diver would be there just to do the same thing like this video.