Fer-de-Lance (1974) on Netflix

Plot summary

An American submarine puts to sea from Tierra Del Fuego with a secret cargo: a container of poisonous snakes that one of the crew has smuggled aboard without telling the others. The snakes leave their storage and bite key personnel, and those bites lead to a mishap that cripples the submarine and sends it down to the floor of the Southern Ocean. Trapped inside the sunken vessel, far below the surface, the crew sets about finding a way out, and the snakes, still loose in the compartments around them, make every attempt harder.