Before anyone jumps down my throat for seemingly expressing any kind of positivity regarding Pack-In-Video's much-maligned Deep Blue: I only did so in the headline above because I've always liked that PC Engine shmup's underwater setting.
(I've also always liked its overall art style, it should be said, although I fully understand appreciate that I'm in the extreme minority when it comes to feeling that way.)
Anyway, back to the soon-to-be-release PC Engine game--yes, you read that correctly--that prompted me to think about Deep Blue. It's called Atlantean, it's being made by the trio at Aetherbyte (including the administrator of The PC Engine Software Bible) and it looks like a mix of the aforementioned kusoge (in terms of aesthetics) and Sega's Fantasy Zone (in terms of gameplay).
All that said, I'm not sure it's worth the $60 (plus shipping) asking price. It only includes four stages, for starters, and then there's the fact that the system's quality Fantasy Zone port can be had for quite a bit less than $60, last time I checked.
Still, if you're in the market for another PC Engine game, this one may be worth considering.