The members of Trident Diving School hire Barnaby to investigate the death of their colleague. Barnaby meets Carl Everett and his assistant Alice Caldwell who claim to be searching for a sunken treasure. J.R. who is certified in scuba makes dives and searches for clues underwater while Barnaby and Betty do the same on land.
| Name | Type | Role | |
|---|---|---|---|
| Paul Robert Coyle | Writer | ||
| Owen Bush | Guest Star | ||
| James Storm | Guest Star | ||
| Janice Lynde | Guest Star | ||
| Robert Ito | Guest Star | ||
| Charles Frank | Guest Star | ||
| Charles Siebert | Guest Star | ||
| Bill Zuckert | Guest Star | ||
| Hank Brandt | Guest Star | ||
| Cletus Young | Guest Star | ||
| Gary Giem | Guest Star | ||
| Don Gordon | Guest Star | ||
| Walter Grauman | Director |