While investigating the disappearance of research ships in the Aegean, the Seaview is damaged by a bomb. Captain Crane goes ashore, and pretends to be a diver for hire. The Captain meets an ex-diver, now a mute due to a tragic accident, who claims to have seen a "city beneath the sea". Crane gets hired by the "bad guy", but his cover is soon blown. He is taken prisoner and nearly loses his life.
| Name | Type | Role | |
|---|---|---|---|
| Richard Landau | Writer | ||
| Paul Kremin | Guest Star | ||
| Al Ruscio | Guest Star | ||
| Hurd Hatfield | Guest Star | ||
| Peter Mamakos | Guest Star | ||
| Linda Cristal | Guest Star | ||
| Joey Walsh | Guest Star | ||
| John Alderson | Guest Star | ||
| Athan Karras | Guest Star | ||
| Dennis Cross | Guest Star | ||
| Peter Brocco | Guest Star | ||
| John Brahm | Director |