I think he probably learnt from his dad, because the beginning of the first episode is just Jason going 'I'M GOING DOWN TO LOOK FOR THE WRECKAGE OF MY DAD'S SUBMARINE' and then he goes down and then something goes horribly wrong and he ends up in Ancient Greece somehow, but I have no idea why he comes from a family of submariners.

(The Jason/submarine pairing ends in tragedy within the first four minutes of the first episode, I'm afraid.)