This seal can hold its breath for two hours and dive nearly 2km down

Northern elephant seals spend more than 90% of their lives underwater, diving beyond 1,500 metres and holding their breath for up to two hours at a time — longer than almost any other non-cetacean mammal. Between dives they surface for only a few minutes before disappearing again.

— Burney Le Boeuf et al., Diving behavior of northern elephant seals — Canadian Journal of Zoology, 1988