A good Samaritan jumped into Lake Pontchartrain and saved a man whose truck had plunged into the water after tumbling over the side of the Causeway bridge Saturday afternoon.

The accident happened a little after 3 p.m. on the southbound span, said Carlton Dufrechou, the Causeway’s general manager.

The driver of a GMC Sierra was reaching for his cellphone about 2 miles from the south shore when he lost control of the truck, Dufrechou said. The Sierra hit a curb and rode a railing along the bridge for about 80 feet before falling over the side, he said.

The 26-year-old driver, a River Ridge man whose name was not immediately available, was able to escape the vehicle.

A passing motorist who had a life preserver jumped into the water and tossed the vest over the driver, Dufrechou said.

Other drivers who stopped to assist hoisted both men to safety after tossing them a rope.

The man in the truck was taken to a south shore hospital to be treated for minor cuts.

No one else was in the truck, and no other injuries were reported, Dufrechou said.

“The good news is everybody is OK,” he said. “That good Samaritan did great.”

The southbound bridge was closed for about 40 minutes during the rescue.