An Aquanox wannabe with twitchy, unadjustable controls, a horrible view/camera system, no documentation/hints/getting-started mode, an infuriating save system, and enemies that half the time you can't see before they instantaneously blow you bits.
If you like the premise (underwater rover/fighter, exploration, et al), go buy a yesterday's-news PC ("top of the line" from 2000-2002 should be fine) and track down a copy of Aquanox; it's a thousand times better done, with really nice music and graphics that blow Deep Trouble out of the water (seriously. It's breathtaking) and an actual plot line.
The control system is horrendous (you don't even get sensitivity adjustments and it is very twitchy).
There are absolutely no explanations about how to use even the one weapon you're given when you start. For example, are your torpedos fire and forget? Will they home themselves onto new targets? Nope! But nowhere will you find that mentioned.
The water is so cloudy you can't see enemy ships until after they've fired at you. Some are apparently equipped with weapons that are impossible to see/avoid; on the first level, I couldn't even tell why my ship kept exploding. The view is, for some incredibly stupid reason, fixed in 3rd-person camera mode, and the camera is ALWAYS putting the view of the ship in the way of where you're going or what you're (trying) to shoot at.
Your shields arbitrarily stop/start "recharging". They seem hopelessly underwhelmed compared to the first "baddies" you meet. You have no way of telling where incoming torpedos are coming from. It's damn near impossible to aim/get a lock on enemy ships.