AllMovie

The Seaview takes on a joint mission with a pair of Russian scientists to salvage the remains of a wrecked Soviet undersea lab, which was destroyed by huge schools of migrating whales. When one of the team is killed in an accidental collision with a whale, the surviving scientist, Dr. Katya Markhova (Gia Scala), insists on making a last-ditch effort to examine the wreckage. Admiral Nelson (Richard Basehart) won't risk another man, and decides to accompany her himself on the dive. But the dive is interrupted by the arrival of a huge sperm whale, which swallows the entire bell. Captain Crane (David Hedison) manages to get the whale sedated sufficiently so that it comes to a temporary rest on an undersea plateau. He has hope that the admiral and Dr. Markhova could be alive if the bell is intact, and decides mount a rescue mission -- inside the whale.