An elephant seal on a determined but inadvisable path onto Highway 37 — and away from San Pablo Bay — snarled traffic Monday afternoon as it tried to cross the road near Sears Point, CHP officials said.

The massive marine mammal was first reported in an eastbound lane of the highway just after 1 p.m. near its junction with Highway 121, the CHP said.

Motorists stopped and tried to shoo it back toward the water, but the effort did not work and instead appeared to frustrate the animal.

“He was not happy with that,” Officer Andrew Barclay said. “It turned from calls for a (seal) in the road into calls of a (seal) attacking cars.”

State Fish and Wildlife wardens responded to the scene and helped shepherd the animal — believed to weigh more than 500 pounds — back toward the tidal waters.

But the elephant seal appeared determined to try again, although there is no water for the animal where was headed north of the highway, Barclay said.

“He is very committed to cross Highway 37,” Barclay said from the scene. “He’s swimming in circles, popping out of the water, staring at me very grumpily because I’m in his way.”

Barclay said traffic moved slowly as motorists gawked at the scene.

Sausalito-based Marine Mammal Center staff arrived at the scene just after 2:30 p.m. to assist in the effort to help the animal. A center representative said the female elephant seal was back in the water and rescuers were making plans to prevent it from returning to the highway. By nightfall, the animal appeared to have hauled out on a mud flat in the area. By that time, the outgoing tide was making it difficult to access the bayshore, putting up another obstacle to the roadway.

You can reach Staff Writer Julie Johnson at 521-5220 or julie.johnson@pressdemocrat.com. On Twitter @jjpressdem.