Underwater Tunnel (海底トンネル, Kaitei Tonneru?) is a location in Final Fantasy Dimensions. It's located to the west of Tower of Trials and it links between this area and the isolated Abyssal Shrine.
The Warriors of Darkness receive a warning from a mysterious voice right after entering this tunnel. However, they ignore it make it through here and come to an isolated area where the Abyssal Shrine is situated.