Lunatan: 10,000-nen no Himitsu

In the anime's story, there was a prospering civilization thanks to giants called Luna who once brought the energy known as Mana. However, a giant tsunami struck the world and destroyed the civilization. The story takes place underground 10,000 years after the tsunami hit. The main characters are Mokugyo (voiced by Katsuyuki Konishi), a fish named with plant life growing from his back, and a talkative creature named Toriiruka (Tomoko Kaneda). The lonely, needle-covered animal named Harry (Kazutomi Yamamoto) and Yona (Houko Kuwashima), a descendent of the ancients entrusted with with the rebirth of civilization, join the group. Mokugyo and Toriiruka may be able to safely return above ground. (Source: ANN)

Trailer