Kaitei Sanman Mile
Japanese title: 海底3万マイル
Alternative titles: Kaitei 3-man Mile, 30,000 Miles Under the Sea, Thirty Thousand Miles Under the Sea
Type: Movie
Source: Original
Episodes: 1
Status: Finished Airing
Aired: Jul 19, 1970
Duration: 59 min
Rating: G - All Ages
Studios: Toei Animation
Genres: Adventure, Fantasy

Returning home from an ocean trip, young Isamu meets the beautiful sea-dweller Angel on a volcanic island. Attacked by a fiery dragon, Isamu and Angel escape on the observation boat See Through, and Angel invites Isamu to see her undersea kingdom of Atlas.

(Source: AniDB)