This is the remarkable footage from cameras attached to under-threat polar bears off the coast of Alaska.
It shows them hunting, play-fighting and swimming in the Beaufort Sea.
The footage was gathered by wildlife biologist Anthony Pagano and the United States Geological Survey (USGS) as part of a research project.
The study revealed the rate of polar bears' energy use is higher than previously estimated.
Experts say climate change has melted sea ice and reduced opportunities for polar bears to find prey such as seals.
This leaves them at risk of expending more energy — in the pursuit of food — than they can obtain, said John Whiteman, writing for Science.
Wildlife eco-physiologist Terrie Williams, co-author of the research, said five of the bears lost body mass during the time they were studied.
"They are spending so much energy walking to find their prey that the energy gained once they find a seal is not enough to maintain their weight," Williams said. "Think of having to drive all over town to locate a gas station for your car only to find that you cannot fill your tank. Eventually, you run out of gas."