You should talk to him mostly to determine how both of you wish to play. You have expectations and he has expectations as well. They may be different and you need to discuss to understand each other and get on the same page. It's his PC so it may or may not be how he wishes to play.
One thing...
Another submarine rpg is Terra Incognita where the PCs are members of NAGS Society (National Archaeological, Geographic, and Submarine Society). Think National Geographic Society as a secret agency in a Jules Verne style setting.
Here's it's site: Terra Incognita: The NAGS Society Website