While covering a test of guided torpedoes, two reporters believe they see what appears to be a strange-looking swimming creature. They investigate the matter further and discover that there is a race of fish-men living under the sea. The fish-men capture the pair and keep them prisoner in their underwater city.
| Actor | Role |
|---|---|
 Sonny ChibaKen Abe | Ken Abe |
 Peggy NealJenny Gleason | Jenny Gleason |
| FFranz GruberCommander Brown | Commander Brown |
| AAndrew HughesNot listed | Not listed |
| EErik NeilsonDr. Moore | Dr. Moore |
| MMike DaneenDr. Josef Heim | Dr. Josef Heim |
| BBeverly KellerNot listed | Not listed |
| GGunther BraunSubmarine captain | Submarine captain |
| KKoji MiemachiNot listed | Not listed |
| TTadashi SuganumaNishida | Nishida |
 Hideo MurotaHenchman | Henchman |
| OOsamu YamanouchiNot listed | Not listed |
| KKosaku OkanoNakamura | Nakamura |
| IIchiro MizukiNot listed | Not listed |
| AAkemi FujiFemale researcher | Female researcher |
| EEnver AltenbayNot listed | Not listed |
 Hans HorneffBill | Bill |
| SSteve QueensCaptain Bob | Captain Bob |