Which of the following mammals can hold its breath the longest when under water?

Beaked whales (Ziphiidae) belong to a family of around 20 species of medium-sized toothed whales. Because these cetaceans spend most of their time far from shore or deep in the ocean, very little is known about them..

Depending on the species, beaked whales range in size from 13 to 42 feet (4-13 meters) long. Their weight can also vary, from 1.1 to 16.5 tons (0.98-14.76 tonnes). Their key distinguishing feature is the presence of a 'beak', similar to that of dolphins. Beaked whales are unique among toothed whales in that most species only have one pair of teeth. The teeth are tusk-like, and only visible in males.

While searching for food, deep-diving mammals face multiple challenges in connection with breath-holding, water pressure, and decompression. To last for long periods underwater, marine mammals often rely on large stores of oxygen and a slow metabolism. Beaked whales have other adaptations which facilitate deep dives, for example: enlarged spleens and livers, and body shape.

Cuvier’s beaked whales, in particular, are master divers, and hold the record for deepest known plunge by a marine mammal. In March 2014, a study revealed that the whales were capable of diving to depths of 1.9 miles (nearly 3,000 m). The species also holds the record for the longest dives. In 2020 researchers, using GPS tagging, recorded the longest deep dive on record: a Cuvier’s beaked whale remained underwater for 222 minutes (3 hours and 42 minutes) without coming up for air.