The weather was clear and the fish were aplenty early on Labor Day.

Then, Port Washington resident Rob Ioanna heard a splash.

Ioanna turned to see the long, sleek body of a whale swim by about 500 yards from his brother-in-law's boat near Execution Rocks lighthouse in the Long Island Sound. Ioanna, 37, and Tim Bischoff, 43, also of Port Washington, almost didn't believe what they had seen.

"I saw a fin sticking out of the water," Ioanna, 37, said. "I said, 'I think we just saw a whale over there.'"

It spouted and it splashed as the men looked on, taking photos and videos after they alerted police to the whale's presence. By the end of their fishing trip several hours later, Ioanna said they had captured more photos and video footage than fish. The whale did not appear to be in distress.

Bischoff said they aren't sure what kind of whale they saw, though after viewing YouTube footage and photos online, their educated guess is that it was a humpback whale. Humpbacks have a distinctive breaching style and long front flippers.

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No matter what kind it was, though, Ioanna said the experience was memorable -- in 25 years fishing in the Long Island Sound, the Bischoff and Ioanna hadn't seen anything like it.

"Everybody was kind of astonished," Ioanna said. "It was truly a blessing to see something so magnificent."

The sighting comes a week after a confirmed humpback whale was spotted off the coast of Milford, Connecticut. Joe Schnierlein, a marine expert at the Maritime Aquarium in South Norwalk, Connecticut, told Newsday on Wednesday that whale sightings in the Long Island Sound are rare, with his records indicating about five of any kind since 1970 and three of those this year alone.

Schnierlein said high concentrations of fish might be behind the increased sightings. Three beluga whales were spotted in May in Manhasset Bay and a minke whale was seen near the Connecticut coast less than a week later. Then came the humpback, seen breaching on Aug. 30.

"As far as that humpback, it could disappear in one day," Schnierlein said. "But I wouldn't be surprised if it's somewhere in the Sound."