On a recent scuba dive through the murky waters beneath the Tramp Harbor dock, Islander Karlista Rickerson discovered a creature she’d never seen before.

The orange plated tunicate, a marine invertebrate, was tucked inside a cement block. Rickerson, 75, and her two dive buddies, Mary Kelly and Peter Wojcik, were thrilled to discover a native species — Chelyosoma productum — under a dock that’s seen a decline in sea life in recent years.

Rickerson and Kelly took closeup photos of the tunicate, some of the best shots of the creature to date, according to Northwest Dive News.

“I was curious,” Rickerson recalled of the tunicate sighting. “It doesn’t look like an anemone, maybe a tunicate, but nothing I’d ever seen before. I thought, ‘This is new. This is different.’”

The identification of the tunicate — with the help of author Andy Lamb — was just the latest in a long string of contributions Rickerson, a retired nurse, has made to the local scuba and marine science communities.

For the difference she’s made in the local dive community, Rickerson was named Diver of the Year by Northwest Dive News and Dive News Network last month.

Her work in the water runs deep. She dives for pleasure but also to help scientists, organizations and the local community better understand the underwater conditions and creatures off the shores of Vashon and Maury Island.

Rickerson, a warm woman with a bright sense of humor, is an underwater data collector for both the University of Washington and Public Health — Seattle & King County, gathering water samples and mussels.

She’s served in many roles at the Washington Scuba Alliance, including several years as its president.

And here on Vashon, Rickerson has educated Islanders young and old about the critters that inhabit the deep — holding show-and-tells at local schools and Vashon Community Care and participating annually in the Low Tide Festival.

“She’s influenced a lot of people,” Wojcik said. “She’s very knowledgeable — always ready to teach you something and point out things you may have missed. She seems to be a really positive influence, too, on the dive community. She really encourages people.”

Rickerson began diving in 1980, when her son David treated her to a Mother’s Day dive off Sandy Shores. After a hip surgery four years ago, she was glad to return to the water. She says she continues to dive because she finds excitement in the underwater environment.

“Some people go water walking or work out in the pool or go to the athletic club,” she said. “I go underwater. … We always find something new, something different.”

Rickerson has dove from various Vashon and Maury sites — Tramp Harbor, Sandy Shores and KVI beach, to name a few. She’s familiar with features of the underwater landscape that some Islanders have never heard of, from the bottle garden at Tramp Harbor to the reef at KVI.

She often brings with her an underwater camera, a gift from her husband Doug, and captures in photos the unusual and exotic sea life she sees beneath the surface.

The beauty of diving, Rickerson said, is it’s an all-year activity.

“You don’t have to wait for the snow; you don’t have to wait for the summer sun — the water’s always there,” she said.

Her most memorable dive came after a show-and-tell session at the Tramp Harbor dock, when a blind teenager dropped his cane into the water. Rickerson retrieved the cane from the deep.

Rickerson has worked hard to see marine areas, including the Maury Island Aquatic Reserve, protected for use by divers and other communities, said Bruce Higgins, the 2009 recipient of the Diver of the Year designation.

“Karlista has been involved in diving for quite a long time, and not just in diving but in a leadership role,” Higgins said. “I think it’s great she got the award. It’s a recognition that we as a recreational community need to remind ourselves that things don’t happen by themselves.”