A Chappaquiddick man and his truck were safely rescued from the Edgartown harbor late Monday morning after the man drove off the ferry ramp on the Chappy side and landed in the water. The incident prompted an immediate call to emergency responders including police, fire and rescue, and attracted a small crowd around the harbor on Memorial Day.

Benjamin Knight, 35, was quickly pulled out of the chilly harbor water and was not seriously injured, officials said.

Edgartown police said Mr. Knight drove his truck, a silver Toyota Tacoma, into the water intentionally. He will face criminal charges and possible loss of his driver’s license in connection with the incident and on Monday was being held at the Martha’s Vineyard Hospital for a mental health evaluation, police said.

The Chappy ferry was on the Edgartown side of the harbor at the time of the incident, which took place at about 11:25 a.m.

Deputy assistant harbor master Michael Hathaway was in the area and saw the incident happen, Edgartown fire chief Peter Shemeth said. “He was able to rescue the driver and also to put a line on the vehicle before it sank and got it out of the Chappy ferry slip,” Chief Shemeth said, noting that this was a critical move so that rescue equipment and the tow truck could cross over to Chappaquiddick on the ferry.

Incident happened near high tide; the truck drifted away from the ferry slip and toward the Edgartown lighthouse.

Mark Lovewell

Incident happened near high tide; the truck drifted away from the ferry slip and toward the Edgartown lighthouse.

Mark Lovewell

Speaking to the Gazette by phone several hours after the incident, Mr. Hathaway said he was nearby at the time, patrolling the harbor in the harbor master’s pump-out boat.

“I seemed to have noticed this truck on the Chappy ferry side that was going a little fast coming down the ferry line,” he said. “And I said to myself, ‘There’s no way this guy is going to slow down at all.’ All of a sudden there he goes, he’s airborne.”

Because the ferry ramp is at a slight incline, Mr. Hathaway said, the truck went into the air about 15 feet, then went out about 20 to 25 feet into the harbor. “As soon as he hit the water I flew over there,” Mr. Hathaway said. He said Mr. Knight got out of the truck through an open window on the driver’s side of the truck, stood on the truck, and was able to climb into the boat.”

He said he dropped Mr. Knight off at Memorial Wharf and at that time, the harbor master patrol boat came on the scene and Mr. Hathaway left to do other work. “I did what I could do, no need for me to be around there anymore,” he said. “They got the gentleman, know where the truck is.”

Mr. Knight told officers that the gas pedal had become stuck and he could not stop the truck, Det. Sgt. Christopher Dolby said in the police press release. But an investigation showed there was no mechanical issue with the truck and it was standard transmission, Detective Sergeant Dolby said. And video footage showed that Mr. Knight circled the ferry parking lot twice before driving off the ramp. “Officers concluded this was an intentional act,” he said.

Fire department diver Eric Willoughby.

Mark Lovewell

Fire department diver Eric Willoughby.

Mark Lovewell

Mr. Knight was taken to the Island hospital for medical evaluation, police said. At the hospital, staff determined Mr. Knight was not injured and he was committed for further evaluation.

He will be criminally charged with a number of motor vehicle violations and disorderly conduct, police said. An immediate threat notification was being made to revoke his driver’s license.

Once Mr. Knight was pulled from the water, the fire department began work to recover the truck. A rescue truck and dive bus were sent over to Chappaquiddick, and fire department divers went into the water while the harbor master’s boat maintained the perimeter.

When the pickup truck was just off the beach at the Chappy Point, officials attached a line to the front of the pickup truck to the rescue truck and using a winch, pulled the submerged truck out of the water.

Harbor master boat patrolled the scene while fire department retrieved truck.

Sara Brown

Harbor master boat patrolled the scene while fire department retrieved truck.

Sara Brown

Chief Shemeth said it was important to get the truck out of the water for environmental reasons, so that fuel and other chemicals would not leak into the harbor.

Diver Eric Willoughby said conditions were favorable for retrieving the truck. “Nice clean, clear water,” he said.

The water temperature in Edgartown harbor is just above 60 degrees.

Mr. Willoughby was in the driver’s seat as it was pulled on land. When the pickup arrived on shore, the passenger side door was opened and water gushed out of the truck.

Crowds gathered at Memorial Wharf and Chappy Point to watch the scene unfold.

The sky was cloudy, the wind steady and cool out of the southwest and the tide was running from the harbor toward the lighthouse.

Stever Aubrey, a health care executive from Dedham, was on the front porch of a family home on North Water street just two piers north of the Edgartown ferry slip.

“I was looking across, right at the Chappy ferry ramp, and saw the truck topple over the edge of the ramp. No Chappy ferry there. It floated there for a number of minutes,” Mr. Aubrey said.

He said Mr. Hathaway arrived with the pumpout boat about two minutes after the incident.

“The guy climbed out that window and Mike got him on board his boat,” Mr. Aubrey said. “And then they tried to wrangle the truck, which was drifting, floating toward the outer harbor. It looked like they were trying to get a rope around it, but to no avail. The thing finally sank after several minutes. But we were glad to see that he was out of the truck safely, through the window and out onto Mike’s boat.”

Witnesses said that as soon as Mr. Hathaway realized the truck was going down, he untied the lines that held the truck to the pump-out boat. The risk was that the truck would pull the boat down with it or rip out the transom.

After the truck sank, Mr. Hathaway took the driver to Edgartown Memorial Wharf, where an ambulance and police cars had arrived and parked, witnesses said.

Chappy ferry owner Peter Wells said he was at home when Captain LaMarche of the On Time III called by radio shortly after 11:15 to say that a car had driven off the ramp on the Chappy side and that his ferry was on the Edgartown side. “I said what I always say when there’s an emergency,” Mr. Wells said: “Repeat that.”

Mr. Wells then called the Coast Guard, the next step in the protocol on the unusual occasions when an accident involves the ferry, its wharves or equipment. He reported that the driver was safe and the ferries undamaged.

Jeff Fager with his wife Melinda Fager watched the divers and other emergency workers locate the truck, raise it and haul it onto Chappy Point.

“As I think back on it, it’s remarkable how well these people responded,” Mr. Fager said. “All of the fire and rescue units that were there. It just happened so quickly.”

A crowd had gathered on the point but “there wasn’t much to say. This was more action than we’ve had on Chappaquiddick in a long, long time. It gathered quite a crowd, because look, we have a quiet little island, and things like this don’t happen very often. So everybody stopped to watch that pickup come out of the water.”