Beluga whales were sighted Friday in what may be the first such visit to Long Island's shores, authorities said.

The three white whales had a "close encounter" with one North Hempstead Town official after boaters spotted them breaking through the waters of Manhasset Bay about 6 a.m.

"They were close enough to me that when they expelled air, I was sprayed with water," said Mal Nathan, North Hempstead Town's chief bay constable. "It was pretty cool.

"They seemed to be feeding and behaving normally."

Early Friday, a worker in a dock-building crew reported a "white speck" in the waters to his colleagues, who didn't believe him -- until hours later, when the specks swam close to their work barge. "We said, 'Cool, look at that,' and then we apologized to the guy we called an idiot," said foreman Tom Denis of Island Park.

Belugas usually don't venture so far south from Alaska and Canada, but one was confirmed as far south as the mouth of Delaware River in 2005, according to the National Oceanic and Atmospheric Administration. The three were first reported May 10 in Rhode Island, NOAA said.

Using the public's photos, researchers in Canada identified one whale as a male from the St. Lawrence River population, a much studied group, said Mendy Garron, NOAA's Northeast marine mammal stranding coordinator. In December, Canada listed this whale group as endangered because its numbers had dropped from 1,000 in 1980 to 900 in 2012.

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The male's companions are also believed to be from the St. Lawrence; all are juveniles, less than 8 feet long, Garron said. Adults can grow to 20 feet.

The closest to Long Island a beluga had ever been spotted was Narragansett Bay, Rhode Island, last summer, she said.

"We really don't know why they venture down here," she said. "They stay here for a week or two and then go back offshore." One theory is that they may be following cold currents, which suit their food: fish that school such as herring.

NOAA has tapped the Riverhead Foundation for Marine Research and Preservation to monitor the progress of these social, curious creatures.

Authorities are worried for their safety during Memorial Day weekend, warning the public to stay at least 150 feet away.

The Riverhead Foundation for Marine Research and Preservation plans an aerial search for the whales today, hoping to take photos and gather data for NOAA. "You can look down on them and see anything that might be noticeable or remarkable," said Rob DiGiovanni, the nonprofit's executive director. Sightings may be reported to its hotline, 631-369-9829.

Nathan said the whales came right to his 17-foot vessel, bumping it gently. Together they drifted for an hour, he said.

"They definitely approached the boat," he said. "I cautiously moved away from them, and after a while they moved toward me again."

He said when he left, they were headed to the Long Island Sound: "I'm going to remember this forever."