I made Dive Sub in less than two days while visiting my family, so I could challenge my brother's kids to something I'd made myself (after losing at more popular titles!).
The game is inspired by Swing Copters, but with a new single-button control mechanic. Press and hold the left mouse button to sink faster and aim for the gaps, even though you can't change the sub's heading. It rewards patience and timing!
Originally a smartphone game, but it works fine with a mouse - see if you can get the timing right and beat my best score (which is 23 on the mobile version).
Hopefully I'll find time to upload it to the app stores (just for the sake of it, I doubt this would make much money!).
Music from Kevin MacLeod's excellent collection - http://incompetech.com/