The homeowners' daughter was taking out the trash around lunchtime when she came face-to-face with the bear.
She quickly retreated and then watched and filmed from a safe distance as the animal munched on some trash, scampered around the backyard and then went for a swim.
FULL VIDEO: Bear takes dip in La Verne pool
Full video: Bear takes backyard swim in La Verne
It seemed to enjoy its time in the pool, cooling off for a while, and then, after a few slippery, unsuccessful tries, hauling itself up by its front legs to an upper section of the pool. It eventually wandered off.
Homeowner Shelley Nobbs said the encounter was quite a thrill for her daughter.
"It was scary for her but she was amazed at the bear feeling so at home in our back yard," Nobbs said.