A humpback whale with an apparently broken back has been spotted in waters near Hawaii, a newspaper reports.

Gerry Charlebois, who takes student pilot/tourists for coastal excursions in ultralight aircraft, spotted the injured whale from the air Monday in shallow water near Kauai.

"He wasn't moving his fluke and was just staying near the surface and sort of limping down the coast," he said. "It's kind of sad to see a full adult whale in that condition. ... It's definitely something he's not recovering from."

"This is one of the most disturbing sights I've ever experienced while photographing whales," Charlebois, the owner of Birds in Paradise Flight School, told The Garden Island Newspaper. "It was freaky. The whale was bent in half. Obviously some kind of blunt force trauma on the side. The poor guy was in trouble."

A large boat or ship must have struck the whale, which hasn't been seen since Monday, he said. Humpbacks normally are pretty agile, so this one may have been old or sick an unable to move out of a ship's way, he said.

Birds in Paradise manager Kirk Johnson said Charlebois and others on the flight first thought they'd seen an albino whale, but when they came around to take another look, they could see that it was discolored instead.

Ed Lyman of the Hawaiian Islands Humpback Whale National Marine Sanctuary on Maui told the paper the whale appeared to be in poor health - emaciated, shedding skin and surrounded by parasites - and there is no established method for euthanizing a large whale.

These big whales tend to die slowly, Charlebois said. When they do, they sink to the bottom until decomposition gases make them float to the surface, where they attract large numbers of hungry sharks, he said.

"It's amazing to see these 15-foot sharks all feeding on a whale," Charlebois said. "You don't want to be snorkeling around there. You don't want to be in that neighborhood."

Charlebois said he and his three other pilots would look for signs of the injured whale again today.

About 2,000 humpback whales live in the waters off Alaska, and many of them migrate to Hawaii's warm waters between November and May, according to Earthtrust.org. Whale watching is a major part of Hawaii's tourism industry. Adult humpbacks range in size from 35 to 48 feet, and weigh about 1 ton per foot.