When a dolphin swam into Bolsa Chica sometime before noon Friday, the wetlands got a surprise visitor.

Now, they may have an unintended mascot. Five days and many media stories later, the dolphin still hadn’t left the water near Warner Avenue and Pacific Coast Highway.

Jim Milbury, a spokesman for the Pacific Marine Mammal Center in Laguna Beach, said the animal was still splashing about Wednesday.

“When I went by this morning, about 6 a.m., he was still there,” Milbury said.

Authorities, he said, had stuck with their plan to let the dolphin leave when it’s ready.

“We’re letting him do his own thing,” Milbury said. “You can’t always tell what their health is just by looking at them, but from what we can see, he’s healthy.”

Kelly O’Reilly, a biologist for the state Department of Fish and Game, urged people to observe the dolphin from marked trails and not venture into the water.

“It is a wild animal, after all, and wild animals can become unpredictable,” she said.

The National Marine Fisheries Service, a branch of the National Oceanic and Atmospheric Administration, has final authority over whether and how the dolphin is removed from Bolsa Chica, O’Reilly said.

The dolphin may have been bullied and prevented from leaving by fellow dolphins, according to one marine mammal rescue specialist on the scene earlier in the week.

When rescue crews on paddleboards tried to help the common dolphin out of the Huntington Beach nature reserve and into the open ocean Saturday, it was aggressively attacked by small group of peers thrashing in the water and was forced back into the wetlands, said Peter Wallerstein, director of the El Segundo-based Marine Animal Rescue.

“He was scared, he was intimidated, he was bullied,” he said.

“Dolphins can be very aggressive toward each other,” Wallerstein added. “They’re not the sweet, loving, gentle animals portrayed by the movies and the cartoons. They do have a dark side.”

That behavior played into the decision by crews Monday to hang back and let the dolphin return to the sea on its own rather than try to guide it into a possible confrontation.

On Monday afternoon, the dolphin could be seen feeding on fish. The animal has a way out of the wetlands even at low tide, rescue crews said. But for whatever reason, it had chosen to stay.

Dolphin expert Dennis Kelly, a marine science instructor at Orange Coast College in Costa Mesa, said the situation has few precedents because common dolphins usually swim in large groups offshore and rarely, if ever, make forays into harbors or channels.

“This is unheard of,” he said.

Kelly also disputed the notion that the dolphin was bullied by his peers.

Though dolphins are known to whack one another with their tails during disputes, he said, “I don’t really think there’s bullying in the dolphin world.”

Instead, the wayward dolphin’s peers were reacting to its strange behavior and unwilling to leave without their companion, Kelly said.

“This guy’s in an unusual place under unusual circumstances. He’s not used to shallow water near shore,” Kelly said. “When there’s a dolphin that is separated from its fellow dolphins for some reason, the others tend to stick around until they know it’s dead, and if it’s not they’ll hang around. This can go on for days.”

The dolphin was first reported in Bolsa Bay early Friday morning. By noon, more than 50 spectators lined the shores to watch the drama, some of them lured by chatter on social media. They snapped photos on their smartphones, set up tripods or just sat and watched.

Lori Graham, who lives nearby, said she came over to the bay with her daughter and sister when she heard a helicopter overhead. “I’ve seen seals but never a dolphin here,” she said.

Heather Swett, another local and a self-described dolphin lover, was on her daily jog near the wetlands when she saw the crowd.

“I feel bad,” she said, standing on a bridge over the water. “I want to help somehow.”

tony.barboza@latimes.com; michael.miller@latimes.com

Twitter: @tonybarboza, @michaelmillerhb