Great level design. I like the atmosphere of an underwater military base where something went wrong. Reminds me of one of the missions in the first Deus Ex.
But the shooter is very primitive. It lacks impact. I think it would be better if there was a shotgun, even if it didn't kill all the enemies with one point-blank shot, then at least stun them. And it would be even cooler if the corpses of enemies remained on the level, and didn't disappear in a bloody fog.