Why did he say it?
Some say people with guilty consciences let the truth out in a disguised way. Unconscious guilt.
Or, he was preparing us for bones and clothing to surface near the shark feeding place,,just in case.
Or maybe by design he let this out, sort of a hint.
The problem though is that he never mentions any of them getting out of the car to 'look at the sharks'. Instead he has them driving back to drop her off because she is sleeping in the car.
Is she sleeping or is she dead?