The Deep Dragon is a sea-dragon. It only appears in Super Darius II game.
Probably the first thing you will notice about Deep Dragon is that he, too, is a biggie of a boss. He moves up and down in a vague piston-like motion, and can crowd you often. His snout looks like a potent cannon, and it is. Watch out. Then come the dorsal missiles, as Deep Dragon moves down and fires them at you. As he moves back and up, he will fire a few more shots at you from his belly and then a biggie beam from his flipper (a potentially lethal attack, mind you). Fortunately, he changes colour with increasing damage, so you can know when he's going down