Grizzly bears do not make cuddly pets, but you would be hardpressed to remember that while watching a large mama bear ferry her two furry cubs across a wide lake.

Video shot by David Roseman, who works in Wood Tikchick State Park in southwestern Alaska part-time, shows a clear view of the bear using its strong legs to propel itself into the water. With small bear cubs, only a few months old, sitting perched atop its back, the mother ferries them to the shore.

"I was heading to do a fuel run for the lodge and just saw something in the distance. I was probably within 30 yards," said Roseman.

Roseman has worked in the park for 21 years, but in the time he's been there, he's never seen cubs float across a lake on their mother's back.

Despite their large hefty bodies and thick fur, brown bears are great swimmers.

Wayne Kasworm, a grizzly bear biologist with the U.S. Fish and Wildlife Service, explained that bears' high fat content and oily coat helps them easily stay afloat. The bears, which he estimates to be about six months old, will likely start to swim on their own once they reach 30 pounds.

Read the rest of the story and watch the video at National Geographic