Kaitei Sanman Mile
30,000 Miles Under the Sea
Thirty Thousand Miles Under the Sea
海底3万マイル
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)