Trivia: The device Bond uses in the final part of the film to reach Atlantis is known as a Wetbike. This device would not be introduced for public use until 1978, one year after The Spy Who Loved Me was cinematically released.
Trivia: Robert Brown (Admiral Hargreaves) would later replace Bernard Lee in the role of "M" from "Octopussy" to "Licence to Kill".
Trivia: When Q delivers the Lotus to Bond and Anya, Anya greets him with "Good morning, Major Boothroyd." This is the only time in the films that Q's name is given. (His name in the novels is Major Geoffrey Boothroyd.).
Chosen answer: When the nuclear subs have been destroyed, there's an explosion in the control room, and one of the men cries out "Fuel tank!" Liparus has numerous internal fires raging after the battle with her crew. These uncontrolled fires eventually spread to her fuel tanks and ammo storages, one of which explodes in a huge fireball and finally causes Liparus to sink.
I thought the final explosions that sank the Liparus were deliberate self destruction after completing the mission in an attempt to destroy any evidence, rather like when Bolfeld manually triggers explosives after being thwarted in You Only Live Twice.
Liparus sinks slowly, and that would leave her crew plenty of time to evacuate. Angry and armed crew with a grudge against Stromberg.
Jukka Nurmi