Cool concept. An automatic dive/rise at a button press or even as the intro to the level would be nice. You'd still have to keep track of how long it takes to dive when deciding how long to stay down. Possibly other collectibles required to complete a mission aside from treasure to make the decision even harder (i.e. 2/3 shipwreck pieces collected). Treasure could upgrade dive time and speed of movement, making it hard to leave behind for the 'mission objectives.' Also gotta have a spear gun on a line to pull yourself around quick or take down the shark!