If you're looking for anime similar to Marine Hunter, you might like these titles.
Ganbare, a black fish born into a shoal of red fish, tries to fit in amid adventures as he is chased by tuna and must evade the Great Octopus.
Some time ago, the evil Poseidon destroyed the continent of Atlantis and all of its inhabitants - except for two: the green-haired baby Triton, and the mermaid Pipi. Triton was brought by the white dolphin Ruka to the shore of a fishermen's village; and there, he was raised by a kind man for thirteen years. However, the time has come for Triton to learn the truth about his heritage, the death of his parents at the hands of Poseidon, and what he must do henceforth: track down Poseidon and bring peace to the seas again. With the help of Ruka, Pipi and other aquatic friends, Triton sets forth to fulfill his destiny.
No more than a few inches tall, Mini Squid Girl goes about her life at Eiko’s house as normal until one day she finds the mischievous Black Mini Squid Girl sleeping in her bed. With the intruder wanting her rival out of the way, Mini Squid Girl must now dodge remote control trucks, projectile rubber bands and all manner of traps if she wants to keep her place in the house. Then while trekking along the scorching beach, Mini Squid Girl smells something delicious coming from Chizuru’s restaurant and goes to investigate…
Vicky is the only son of Halvar, the formidable viking chief. Vicky renounces violence but nevertheless he is able to convince the seasoned viking warriors to take him along on their voyages. In dangerous situations, where their bravery and force are not quite enough to master the situation, the wild-eyed warriors learn to rely on Vicky's cleverness.
The ruler of the underground world, is planning to conquer the whole world. Riding the fire dragon Isamu and Angel, the princess of the undersea kingdom, try to stop him from destorying their world.
Luffy’s crew is in dire straights: they are in the Grand Line, running out of money fast! In their search for a quick fix, they find out about a Pirates race. Should they survive the treachery of the other pirates and the Grand Line itself, they can net over 3 million belli, making the venture profitable indeed. Of course, they immediately sign up, knowing that if they win their problems will be solved – but the opposition is no joke. Devil Fruit users, merman, huge giants and bounty hunters all stand in the path to their success!