2. Side Quests & Story Missions - Stealth Etc
The ability to put on scuba diving equipment or jump into a submarine and delve into the ocean makes the player a lot more stealthful. This could open up brand new possibilities for missions such as infiltrating a drugs cartel aboard a yacht in the middle of the ocean. You could simply swim up to the vessel, undetected, climb up the sides and open fire. There are other possibilities for story missions too, such as finding and locating a hidden stash of drugs on the oceans seabed for a gangster or making sure something never sees the light of day, like a gun or a knife used in a murder. There's also possibilities for side quests, too. Think of the helicopter tours you got to take in Grand Theft Auto IV, perhaps you could pay to enter a cage that would be slowly lowered into the ocean so that you could view Great White Sharks safe in the knowledge that your health bar wouldn't be taking a hammering, which brings us too...