I like the idea of the game, but the execution leaves a lot to be desired. The controls are awkward, not to mention completely unexplained. I only knew how to play thanks to reading other comments first and a bit of guesswork. As mentioned by others, some ambient sounds or music would have helped fill the dead space considering the long stretches of nothingness at times.
At one point, after hitting a landmine, my character glitched out and just kept facing the same direction no matter what direction I swam in. On a fun note, I got ridiculously lucky in dodging every swordfish by complete chance- until I didn't, haha. Couldn't make it to the end as I ran out of air. I also feel the oxygen tanks are too sparse. I realize there's not much you can do about it right now, but you should definitely update the page with the controls. That will at least alleviate the player frustration at the start of not knowing how to play. You could also take a screenshot and use it as a thumbnail so people will at least see an image while browsing the submissions. Hope that helps!