If you're looking for anime similar to Akubi wo Suru ni wa Wake ga Aru, you might like these titles.
Opening its eyes, the moon that fell to the depths of the sea was met with complete darkness. Will the moon be able to return to its home in the sky?
Teenage Marine Boy battles evil on and under the seas on behalf of the Ocean Patrol - aided by the amazing inventions of his father, Dr. Mariner and the brilliant Professor Fumble. Joining Marine Boy in his mission are his white dolphin, Splasher, young mermaid Neptina, and fellow Ocean Patrol agents Bullton and Piper. Get ready to dive into the amazing aquatic animated adventures of Marine Boy!
The anime centers on three jellyfish named Mizukurage (moon jellyfish), Akakurage (northern sea nettle), and Pacific sea nettle. All three are frequent visitors of the Enoshima Aquarium to the point of all three having annual passes.
Fourteen-year-old Jean was just an ordinary would-be inventor, until the mysterious Nadia crashed into his life. With no family, a pet lion and a jewel known as the Blue Water, Nadia is constantly on the run from those who want to steal her most valuable gem. Now, with a trio of thieves and the nefarious organization known as Gargoyle on their trail, Jean and Nadia must struggle to learn the secret of the Blue Water and protect its powers from those who would use them to destroy the world!