I guess it's not a good idea to make a new game in underwater environments (too boring). But some of those ideas could be incorporated into this game. For example, alien bases on Earth could be located only underwater and require a specifically designed craft/ship to get there and dock to entrance. Also, in 2083, there could be some small human underwater settlements attacked by aliens, i.e. built close to deuterium mining plants for our thermonuclear reactors - most important since aliens interrupted all deliveries from Mars (in Martian underground water tanks there's much greater deuterium percentage then on Earth). Of course, all of these would require whole new, interesting research branches.
Wait, humanity already made it to Mars in this storyline?
Well, we could easily do it by 2083. Although I guess we won't. But, hypothetically, we could build those clumsy ships that look like space stations with engines, some modules for transport from the ground and one mining plant (which could mine enough deuterium for one third of Earth's electrical power needs - thermonuclear reactors are very powerful).
...In long. NO!
So, you'd like the Underwater approach... OK.I thought it could enrich the game's universe, add few interesting research options and add a little (very little, hehe) verity to missions' tactics by placing soldiers at the entrance instead of around the aircraft.
How do you believe that will improve the game experience?
Although DiDiT's avatar makes him look like an irritating moron (no offense, I'm just talking about avatar )
you two just enjoy slapping another one down?
Sorry, but I remember that the devs have rejected underwater/sea/shoreline missions many times.
So you have to do it yourself (DIY) and even then it most likely won't make it into the official branch.
Also, humanity never made it into Mars and we still don't have fusion power (-> need for deuterium for other than research purposes).