Many anime often have episodes that take place at the beach or involve sailing across the ocean, such as One Piece. However, there are also a few that focus on life taking place underwater rather than on the surface.
Some of these anime focused on ships sailing on and/or underneath the sea, including Blue Submarine No. 6. Others focused on the sea life living deep underwater such as mermaids in Mermaid Melody Pichi Pichi Pitch. Either way, all of these anime had engaging stories, characters that developed close friendships or romances with each other, and fun worldbuilding to go along with these fascinating deep-sea adventures.
6 Blue Submarine No. 6 Had An OVA Adaptation
Blue Submarine No. 6 was a post-apocalyptic manga series that was three volumes long. Despite the short length, it also had an OVA adaptation produced that was four episodes long. After the OVA adaptation was announced, the series was revised into five volumes under the name AO6.
The series' story took place in the distant future, where the Earth's oceans rose and flooded most of the sea-lying land. The flooding was caused by the rogue scientist Zorndyke, who also created half-animal hybrids that the rest of humanity had to fight against with its submarine forces. The main protagonist was one of the submarine pilots, Tetsu Hayami.
5 Nagi-Asu: A Lull In The Sea Followed Humans Who Lived Underwater
Nagi-Asu: A Lull In The Sea, also known as Nagi No Asukara, followed seven friends. Some of them came from the sea, such as Chisaki and Hikari, while others came from the surface, such as Miuna and Sayu.
Long ago, humans lived underwater and developed a scale-like layer on their skins called Ena to do so. After several humans decided to live on the surface, however, this led to these two types of humans developing fundamental differences both socially and biologically. This series lasted for 26 episodes and was praised by fans and critics for both the underwater concepts and the love stories involved.
4 Nadia: The Secret Of Blue Water Followed Two Protagonists And Thieves Teaming Up To Stop Neo-Atlantean Forces
Nadia: The Secret Of Blue Water followed a young inventor named Jean and a circus performer named Nadia. The two of them were pursued by thieves so they could obtain Nadia's pendant, also known as the Blue Water. After being rescued by Captain Nemo and his submarine, the thieves and the protagonists joined forces to fight the Neo-Atlantean forces threatening to take over the entire world. Nadia lasted for 39 episodes and also had a feature film sequel released in 1991 in Japanese theaters before being released on DVD in 2002.
3 High School Fleet Had Students On The Run After Accusations Of Mutiny
High School Fleet, also known as Haifuri, followed protagonist Akeno Misaki after she enrolled at Yokosuka Girls' Marine High School to become one of the highly-regarded female marines known as the Blue Mermaids. After an incident with their instructor resulted in them being accused of mutiny, the girls ended up sailing together to find out the truth of their situation while avoiding being pursued by law enforcement. Their journeys sailing together resulted in the group becoming close, tight-knit friends with each other.
High School Fleet lasted for twelve episodes, but it also had two OVA episodes released in 2017 and a film adaptation released in 2020.
2 Amanchu! Followed Two Girls Joining A Scuba-Diving Club
Amanchu! followed a shy young girl named Futaba Ooki who joined the school's Diving Club with the scuba-diving-obsessed Hikari Kohinata, despite Futaba not even knowing how to swim at all. After they both joined the Diving Club and learned to scuba-dive, they became close friends with each other and the entire rest of the club. This series aired for two seasons and each of them lasted for twelve episodes. The first season also had an OVA episode. The manga that the series was based on ended in May 2021 and will ship its final volume in November this year.
1 Mermaid Melody Pichi Pichi Pitch Followed Mermaids With Idol-Like Singing Powers
Mermaid Melody Pichi Pichi Pitch followed mermaid Lucia as she searched for a boy she rescued from a tsunami wave years before the story's current events. She did find him but unfortunately could not tell him that she was the mermaid or else she would turn into bubbles and disappear. Meanwhile, she and her friends also dealt with water demons that were trying to invade the sea world and had to turn into singing idols to get rid of them with their voices. The anime adaptation lasted for 91 episodes - the first season with 52 episodes and the second with 39.