Very nice!
It would be even more fun if it was possible to shoot torpedoes at enemies or to clear the way :-)
The only thing I didn't understand was what the floodlights were for. The idea of spotlights is interesting, and for example, it is used in games such as Sunless Sea, but even without spotlights, I can clearly see the environment. Maybe I just couldn't get down deep enough (so far my record is 600+ meters) to appreciate the benefits of spotlights.
But other than that, it's a simple, but great game.