05/17/2012 at 10:40 AM EDT
Aimee Teegarden, a self-described "beach baby" from California, has seen plenty of marine life – sea lions included – during her many trips out to the water to surf.
But it was her involvement with conservation group Oceana
gave her an experience to remember.
The Friday Night Lights
star recently filmed a PSA for Oceana, and journeyed off the California coast to Santa Barbara Island, where she free dove with sea lion pups in a rookery, or breeding colony.
"I couldn't comprehend exactly what I had signed up for," Teegarden tells PEOPLE. "It was honestly one of the coolest things I've ever done in my life."
Surrounded by a kelp forest and by an overwhelming number of playful sea lions, Teegarden says she felt like Ariel of The Little Mermaid
: "I just wanted to stay down there."
"It was so fascinating to me how personal they would get," she says. "They were so interested in everything. They would swim up, come up right to your face, look you in the eye and do a little somersault and swim away. They were just like little kids."
The resulting PSA shows scenes from Teegarden's five-hour-long, "once-in-a-lifetime experience," and has her calling for the protection of the ocean's "hidden treasures," like the pups she met on her amazing day.