Blue Submarine No. 6 - Season 1 (1999)

Humanity is under constant assault by a terrifying race of sea mutants with only one purpose: eradicating all humans. Mankind's last hope lies with the Blue Submarine No. 6 and her dedicated crew-who have joined together to fight for man's survival.

With Zorndyke's forces held at bay, for the moment, after another undersea battle, Blue Submarine and her crew return to base for much-needed repairs. On base, Tetsu flaunts his lack of respect for authority, while simultaneously getting on Mayumi's nerves.

While Tetsu drifts aimlessly across the open ocean, he sees his life in flashbacks before finally slipping unconscious. When he wakes up, he's surprised (and unnerved) to find himself at the mercy of his own enemy.