I set out to help philhassey's team instead of doing an own entry, but as I rather suck at pixel art, and right now they need NES-style tile and sprite art, this wasn't quite satisfying.
And just now, I happened to have the greatest game idea ever - so I tentatively fired up vim and with a blank file (the "screenshot" is just a mockup, all I really have so far is nothing :P) and might try doing a solo entry.

Well, still all I have is the nautilus, but this time it's an actual screenshot :)

Not much works, basically an OpenGL window which displays a deformed sphere.. but, I also have controls done (using quaternions), and three gauges (compass, incline, horizon) - the horizon I already knew how to make, it would have taken all day otherwise.

Next I need a 3d tilemap, where each cube has one of 6 water flow direction.. and the game will be about guiding the ship up before air runs out. The end of each level will be an air tank, and the surface for the last.

Well, I won't be able to finish, all the huge progress of the last hour or so is a propeller added to the submarine. This leaves a todo list of:

• add side rotors to ship
• turn steering propeller according to controls
• main motor RPM gauge
• altitude gauge
• water currents, levels
• particles to see current direction
• other objects.. plants, fishes?
• surface (texture? sky? fog? light beams? water effect?)
• sound, music, menu, polish