Pretty fun game, but get's a bit boring after a time.
The game is way too slow paced, the best tactic is to just be somewhat far away from the center where the enemies spawn, and the shoot them from far away, and when you get more upgrades, this get's really effective, especially with the shield and dash.
You should make it so the enemies spawn around the player, not just in the center, to make that tactic not work so well and to make the game more fast paced, make a slower torpedo cool down for the player and the enemy subs and maybe make more of them, and increase the speed of the enemies a lot.
Also the camera is kinda bad, it should go with you cursor, so you could check behind you and move at the same time, and that would work really well.
Then the movement, it's like too snappy, the sub is underwater, so in my opinion it should be more icy, some maybe don't like that, but it's underwater, and it doesn't feel like that currently.
Also the movement of the enemy subs is way too fast, some times they start like spinning in place, which looks really weird, they should be only able to turn slowly, and also only turn when moving, so it would look more natural.
Then the weird box structures in the corners of the map, you should make the camera go below them when you get close, or just remove them, because now 90% of the time when you are near them, you don't even see them, because your camera is clipped inside them so you can't see them (that was a lot of "them").
Also the top of the water, it doesn't look like the top of the water at all, I guess it is, because you can't go any farther up and the blue water effect disappears, but like, you can't see the top, you should see it like wavy and cool, also please allow the sub to jump above the water, it would be very fun.
Then the missiles, they are way too hard to see, maybe add some lights to them, so they would glow, like red glow for enemy missiles and yellow for the player?
And the sound effects, there isn't any shooting sound effect, clear dashing sound effect, torpedo and the torpedo explode on enemy sound effect is too quiet, it would feel a lot more satisfying if it was louder, even in little farther distances.
Also the torpedos turn really weirdly, maybe slowing down the turning could help?
Also I survived for 13min 53sec and the score was 1340.