The Vineyard Haven harbor patrol boat sank in its slip Wednesday night, harbor master John Crocker confirmed.

“It was tied up just as we left it yesterday evening, and when I came in this morning it had sunk,” he told the Gazette by phone Thursday.

The vessel is one of many boats in the harbor master fleet and was tied to the dock off of Owen Park. The harbor skiff, which was tied next to the patrol boat, did not experience any problems, Mr. Crocker said.

He noted there had been no foul weather on Wednesday night last night said he was unsure what caused the boat to sink in eight feet of water.

He estimated that the boat, a 30-foot aluminum vessel with dual outboard engines, cost about $250,000. It was purchased through a federal port security grant and is insured, Mr. Crocker said.

He said the police were not notified, and the boat was hauled out by John Packer Thursday morning using a crane and barge.

“We have no details at this point,” Mr. Crocker said. “We brought it to the shipyard. . . they will flush the engines to try to preserve the vessel.”

He said he will be conducting an investigation.