At first, people didn’t believe it. Footage circulating online showed what appeared to be a yellow-bellied sea snake writhing on a Southern California beach. Skeptics quickly questioned whether it was legitimate, with plenty suggesting the clip had actually been filmed somewhere tropical — perhaps Mexico. Turns out, it was real. And it was filmed at Crystal Cove State Beach in Orange County, just north of Laguna Beach. Jackie Aguilar told CBS Los Angeles she spotted the snake while walking with her family last Friday evening. Seeing the sluggish animal struggling onshore, they attempted to help it back into the ocean — before learning what it was. “What? A venomous sea snake on the beach! And I, like, I ran and I just kind of left and I was like, there’s a snake,” Aguilar said.  It wasn’t until later that the severity of the encounter set in. “They’re all telling me like it’s one of the most poisonous ones.…