By day, Sam Fye glistens with sweat, hefting 150-pound bags of cargo on the Red Hook docks.

But when dusk envelops Pier 9B next weekend, the longshoreman-turned-actor will be doused with baby oil to simulate a hard day's work on the Mary A. Whalen barge that serves as a stage for a production of Giacomo Puccini's "Il Tabarro" (The Cloak).

"It's a lot different than actually working," said Fye, 29, of his part in the opera as he lifted bananas off a ship last week. "Acting is harder. You have to think. You gotta pretend to move things."

Fye and six other longshoremen volunteered to be in the production after seeing the opera company start rehearsals, said Matt Yates, a spokesman for American Stevedoring, which employs the longshoremen.

Though the two groups couldn't be more different, they "just clicked," Yates said.

"It was just rough and smooth coming together," he said. "It was these theatrical, camp opera women seeing these burly longshoremen."

To transform the modern-day heavy lifters into 1940s stevedores, the show's costume designer outfitted them in smudged white wife-beaters, caps and blue bandannas and sprayed them with baby oil.

Fye didn't seem to mind.

"I don't mind the oil," said the burly worker, who lives in Red Hook. "It's all for the play - to make me look like I'm working up a sweat."

Dockworker Matthew Ercolano, 28, sounded fairly blasé about his opera debut.

"I've seen opera, but I've never done any acting," said Ercolano. "It's not like I have a part in the opera. I don't say anything. We walk off the boat. We walk on it."

Like their real-life jobs, the dockworkers lift lots of cargo. But 30pounds of wood chips - labeled "cocoa beans" for the production - was certainly not a big theatrical stretch. "I'm used to at least 150, so this is nothing," Fye said.

Because the one-hour opera takes place on a ship and revolves around stevedores, it only seemed natural to bring real workers on board, said Judith Barnes, founder of the Vertical Player Repertory, which produced the opera.

"It certainly made it a deeper, richer experience for us," said Barnes, who also sings the female lead. "We wanted to get these guys involved and connect with them and the place, not just to look at it as a stage."

Yates, the dockworkers and the opera singers also shared "a moment of sadness" last week when legendary singer Luciano Pavarotti died. "Some of the longshoremen are from Europe - where Pavarotti is a household name," Yates said.

After 38 years on the waterfront, Fabian Zabatta, 60, was enjoying his debut as an extra. "It's a beautiful experience," Zabatta said. "The whole thing is very interesting to me - the rehearsals, seeing the opera singers working, the boat, the beautiful waterfront with New York in the background."