The Predator in the Pool - S5-E18
Character mistake: When Bones and Dr Hodgins, who is proclaimed as a seasoned diver in a previous episode, are in the tank, Bones gives an instruction and Hodgins replies with a thumbs up. Since Bones is diving as well, they both would know from certification (without which neither would be allowed to dive in the facility) classes that a thumbs up is the hand signal for "I'm ascending", not OK or any form of acknowledgement. They either are not certified divers or they should have immediately surfaced. (00:06:30)