The small, furry sea otter liked swimming in saltwater, eating seafood, and especially liked catching a glimpse of her reflection in the mirror.

For more than 20 years, Brook the sea otter drew crowds to watch as she frolicked around with longtime companion, Charlie, at the Aquarium of the Pacific.

The Long Beach aquarium on Wednesday announced Brook, who had recently been diagnosed with congestive heart failure by the aquarium’s veterinary team, had died a day earlier on Jan. 29.

Born in 1997, Brook was 21 and was considered the oldest living female southern sea otter in an aquarium or zoo.

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Brook, as a 1-year-old pup, was one of the first sea critters brought to the aquarium in 1998, before the aquarium was open to the public.

“She was known for her photogenic looks and regal demeanor, which secured her place in the hearts of many during her 20 years at the Aquarium,” reads a statement about her death. “She will be greatly missed.”

Long-time Aquarium volunteer and blogger Hugh Ryono recently posted a video of Brook and Charlie as pups frolicking in the Aquarium’s sea otter habitat in 1998.

A memory book has been created for the public to share memories or give donations in her honor.

Sea otters, which once roamed the area in great numbers, are a rare sight after they were nearly hunted to extinction.

Biologists believe that at one time, between 16,000 and 20,000 sea otters could be found along the coast between Baja California and the Pacific Northwest, according to the aquarium’s website.

Sea otters disappeared from the area for several reasons.

First, they were overhunted. The fur trade from the late 1700s to early 1900s nearly brought the animals to extinction, but a colony of about 50 otters was discovered in 1938 in a cove near the Bixby Bridge in Big Sur.

With protection from the North Pacific Fur Seal Convention of 1911, sea otters were granted protection from trapping. They were listed as an endangered species in 1973.

Then, the U.S. Fish and Wildlife Service implemented a program in 1987 that introduced a small species of otters to San Nicolas Island, which is part of California’s Channel Islands, in an effort to protect the federally threatened sea otter.

As part of that program, “no otter zones” were set up, which meant any otters found south of Santa Barbara County were relocated to the north. The U.S. Fish and Wildlife Service terminated the program in December 2012, allowing the otters to swim in their natural range, which was expected to boost recovery of the species.

At that time, the population was estimated at 2,792, according to a 2012 U.S. Geological Survey. In 2014, that number rose to 2,944.

Occasionally, sea otters are spotted off the Southern California coastline.

A whale-watching boat from Dana Wharf saw an otter off the coast of Laguna in December 2011. It was their first sighting in 30 years.

Then, there were a few sightings in 2013 near Huntington Harbour and the Seal Beach National Wildlife Refuge, and in 2016 images showed a sea otter hanging out off Crystal Cove.