Gray Lady Down (1978)

Synopsis
When the nuclear submarine he captains is rammed by a freighter while surfacing in Atlantic waters just off the coast of Rhode Island, Navy Captain Paul Blanchard (Charlton Heston) is able to radio for help. However, his sub's condition calls for urgent attention. Downed in extremely deep water near an even deeper ocean trench, the sub is perched precariously in waters too deep for conventional rescue efforts and is in danger of plummeting into the ocean trench. When the sub's escape hatch is blocked by debris from an undersea earthquake, the situation becomes even grimmer. Despite assurances that all will be fine, Captain Bennet (Stacy Keach), who is coordinating the official Navy rescue effort, has already warned Blanchard's wife to expect the worst. However, another Navy captain (David Carradine), who is working on an experimental deep-sea exploratory vessel for the Navy, hears of the incident and volunteers his help. This story is based on the novel Event 1000 by David Lavalle. ~ Clarke Fountain, All Movie Guide