Voyage to the Bottom of the Sea (1964)

S3E19 The Mermaid

Title: The Mermaid Plot: While the Seaview is busy with an oceanic survey, Captain Crane encounters a mesmerizing mermaid and invites her onto the submarine. Soon, he finds himself enchanted by her allure. However, a menacing sea creature tracks her down, leading to chaos aboard the sub. The situation intensifies when the Seaview receives orders to neutralize a nuclear device secretly positioned near the California coastline, putting everyone on high alert as they navigate both the underwater threats and their mission.