Deep Blue (or Deep Blue - Kaitei Shinwa (海底神話, "Bottom of the Ocean Legend") in Japan) is a horizontally scrolling shoot'em up developed by Hi-Score Media Work and published by Pack-in-Video (in Japan) and NEC Technologies (in North America).

Aliens are attacking Earth. They have used baceria to mutate marine and sea lifeforms which now attack the shores. You take control of the A.N.G.E.L. Fish Attack Sub to fight back.

You have only one life, but you have a health bar. Your health is indicated by the colour of your ship's porthole. Health will slowly regenerate over time. Getting hit will stun you for a short time, you can neither shoot nor collect power-ups. Power-ups are left behind by ocean sunfish. They include health restore, an increase in fire frequency or different weapons. A weapon can be upgraded by collecting it several times. However, you loose a weapon upgrade if get hit.