Let me go against the grain here and say that hockey players have non-human cardio because they train *off* the ice so much.. same with gymnasts and any other athlete.
As divers we should be training out of the water even more than in the water... get in better shape in order to be a better diver in the water... work on relaxation and breathing in order to be a better diver in the water.. IMO you should be getting better at that stuff *out* of the water so that it improves your time *in* the water.. and if you're improving those skills *by being in the water* something is backwards. This should go for any athlete.. train to be better at what you do.. what you do as your sport is not training