Synopsis: It's the future... and the sea level has risen. Humanity is running out of land as the Zorndyke, a new race of water-dwelling creatures, wage war on them. Mankind strikes back with a fleet of its most advanced war submarines -- its most prized and greatest one being the Blue 6. Mayumi Kino is a young pilot from the Blue 6. She is tasked with finding Tetsu Hayami, one of the most skilled pilots in submarine history. Mayumi is to persuade him to rejoin the Blue Fleet. She later discovers that Hayami now works as a freelance salvager, and has no intentions of ever fighting again. But when the Zorndyke suddenly attack, Hayami is forced to work with her anyway...
Review: If you're looking for an uncomplicated, pulse-pounding action anime with spectacular imagery, then look no further. Blue Submarine No. 6 is just perfect for those times when you're craving for some action, with nary a care about the story. This 4-episode OAV doesn't make any visible effort to build the characters and the setting. It's just action all the way. You don't really know what's happening from the start, until you get to some brief explanatory points. Believe me, these backgrounders are shorter than the shortest action scenes (except for the last episode, which is when you get to truly understand Blue Submarine No. 6).
There are two main characters -- Hayami and Mayumi. Hayami plays out his role as the jaded hero perfectly. He is also given more history compared to the rest of the cast. But Mayumi? Heck, you don't even know why or how she came to be with the Blue Fleet. Blue Submarine No. 6 may disappoint you if you prefer anime with a more compelling and coherent story.
However, what Blue Submarine No. 6 lacks in story, it makes up for in graphics. The art and animation, and everything related to the visual aspect, are absolutely superb. Blue Submarine No. 6 is the eye-candy of eye-candies. I kinda get the feeling that this anime was created for the sole purpose of showcasing a new brand of animation -- one that merges cels and computer graphics. While Blue Submarine No. 6 may not exercise those brain cells, it is truly a feast for the eyes.
Miscellanies: I read somewhere that Blue Submarine No. 6 is an experimental venture.