Sea lions swim with up-and-down, wing-like strokes of their foreflippers.

California sea lions are very agile and maneuver well in the water.

California sea lions are probably capable of reaching speeds of 21.6 kph (13.4 mph), but generally cruise at slower speeds, about 7 kph (1.2 mph).

California sea lions usually do not need to dive very deeply, since most of their food is found in shallow waters, about 26 to 74 m (85–243 ft.) deep. They can, however, dive to depths of about 274 m (899 ft.).

California sea lions usually stay submerged three minutes or less; however, they can remain submerged for as long as 10 minutes.

Foraging trips for Galápagos sea lions have been estimated to last an average of 15.7 hours and entail 85 to 198 dives.

All marine mammals have special physiological adaptations for diving. These adaptations enable a California sea lion to conserve oxygen while it is under water.

Like most other marine mammals, a California sea lion's typical respiration cycle is a short exhalation, a short inhalation, and a longer breath-holding (apnea) period. Each exhalation and inhalation lasts about a second. The breath-holding period can last from 12 seconds to 15 minutes.

On land, California sea lions exhibit a variety of sleeping postures. They commonly sleep on the beach with all four flippers tucked under the body or with the foreflippers tucked under but the hind flippers together and extended. They also commonly rest and sleep balanced upright with their heads thrown back, noses pointed upward.

Heat loss in water is about 27 times faster than in air of the same temperature.

A California sea lion's core body temperature is about 37.5ºC (99.5ºF).

California sea lions deposit most of their body fat into a thick layer of blubber just under the skin. The blubber layer insulates the California sea lion and streamlines the body. It also functions as an excess energy reserve. This is especially important for males, because they fast during the breeding season.

Sea lions can lose excess body heat by staying in the water, on damp sand, or in the shade.

A sea lion often regulates its body temperature by lifting and exposing one or more flippers. The blood vessels just under the skin dilate and absorb or release heat to the environment.