I'm curious to see if diving and SCUBA diving will be realistic along with everything else. As most of us know we can't go very deep without our ears hurting and you have to re-pressurize (or clear the negative space in our ear) as we go along because of the crushing forces of the water above. There should be some sort of system implemented into it, for example diving deep fast would rupture your ears and you would no longer be able to hear or if they didn't rupture then for a period of time you would be deaf and if you ascended too quickly your blood would 'boil' and your character would begin to writhe in pain as would be expected. And things like explosives in the water rupturing your ears (and other organs depending on how strong the shock wave is) should be added as well. There's a lot of things that could be added but those are really the big ones and I kind of hope they are as the game is polished more and more.