Quite a few of the fishermen boarding the party fishing boat Skipper in Oak Bluffs on Wednesday morning before 8 a.m. were repeat customers. They toted their own coolers loaded with refreshments, and towels for keeping their hands clean.

Bill Devine’s 50th birthday was two days away. It was an easy decision for the repeat Vineyard vacationer from Hanson to celebrate aboard Capt. John Potter’s Skipper on Wednesday morning. “I like fishing on the Skipper,” Mr. Devine said. “At least once a summer, I like to take the trip.” He brought along a cooler loaded with lunch and a couple of frosty beers on ice. In his pocket he carried an unopened cigar.

Brandon Mack, 12, of Highland, N.Y. was also a repeat customer. In years past he has made as many as five trips in one summer. As he boarded the boat, he told the captain he planned to catch a big one.

The Skipper is a 40-foot wooden party fishing boat that runs out of the Oak Bluffs harbor. When the weather is right the Skipper makes two four-hour cruises a day, all around Nantucket Sound. Mr. Potter has been operating the boat for 23 summers. He charges $50 a head for adults and $40 for children. He provides fishing rods, hooks and weights and bait. And towels.

Wednesday morning saw a gray light rain. Fog obscured the view across the Sound to the Cape. The forecast called for the rain to stop, and it did as the boat engine was turned on. Mr. Potter issued his standard welcome.

“Thank you for flying American. Welcome aboard,” he announced as customers stepped from the dock onto the stern of the boat.

Mate Darren Smidt was also on hand with a greeting.

As the boat headed out of the harbor, Mr. Potter announced the direction: west. Mr. Smidt handed out small plastic bait bowls filled with squid soaked in seawater.

Below decks the 1953 diesel engine roared. Mr. Potter said the 671-horsepower engine just keeps going; they don’t make diesels like this one anymore, he said.

Above the din of the engine, Mr. Potter had a serious announcement: “Please don’t eat the bait until we get to the fishing grounds. Leave the bait for the fish,” he said. “We had one trip yesterday, where the passengers ate all the bait.”

Passengers smiled.

Mr. Potter bought 2,200 pounds of squid in the spring from a local dragger, and every day he whittles away at the load. The squid were caught in Nantucket Sound. Locally caught and prime stuff.

The first stop was one of Mr. Potter’s 60 favorite fishing spots. “I call this place Scup Alley off East Chop,” he said. The water is 30 feet deep. Mr. Potter and Mr. Smidt instructed visitors on how to catch fish.

“You’ll know when it [the weight] hits the bottom, when the line stops coming out. Then reel in the line a little to bring the hook and weight a few inches off the bottom, where the fish can smell and see it,” he coached.

Mr. Smidt showed anglers how to jig the rod up and down so the bait appeared to dance.

Within minutes, party boat guests were hooking fish.

As the fish came aboard, Mr. Potter gave a quick lesson on Massachusetts minimum sizes for fish: 10.5 inches for scup; 12.5 inches for black sea bass.

Diksha Thach, 10 of Medfield, reeled in a keeper scup on the starboard side of the boat, thrilled at her catch.

Opposite her, on the port side, John Audy, 18 of Medfield, was disappointed. “I don’t know how to catch fish. I got to have a harpoon,” he said.

After a few minutes of fishing, the captain announced that he wanted all lines in the boat. “We’re going somewhere else,” he said. The boat headed east, just south of Hedge Fence Shoal. Mr. Potter pulled out a picture of the 282-foot S.S. Kershaw that sank just south of Hedge Fence 81 years ago. The fish love hanging out around the wreck, he said.

Max Haddad of Richmond, Va., was busy keeping his two sons rigged. He and sons Michael, eight, and James, five, had been thinking about going out on the Skipper since last winter. The two things they like to do on the Vineyard? Go fishing on the Skipper and have a lobster at Menemsha.

The fog came and went; the Oak Bluffs waterfront was seldom out of sight. Soon the Skipper was about two miles from the Oak Bluffs Steamship Authority wharf. The water was nearly calm save an occasional wave from a distant high speed boat passing underneath and causing the boat to rock. “Rock and roll,” said Mr. Potter.

With the engine off, the Nobska Light foghorn could be heard in the distance.

For 23 summers Mr. Potter and his crew have made Nantucket Sound their workplace. In the captain’s pilot house there is radar, a colorful fish finder and GPS. Mr. Potter has not only marked his favorite fishing spots on the GPS, he has committed them to memory. When Mr. Potter is off the boat attending to his painting business, John Nelson of Oak Bluffs, a science teacher, steps in as captain. The two know the rituals of operating a party charter fishing boat for the benefit of the customer.

Mr. Audy, who minutes before was complaining of not getting any fish, reeled in his first black sea bass.

Disksha Thach reeled in a fluke just over the minimum size of 18.5 inches.

Scup, black sea bass and fluke are bottom dwellers. They all like to eat squid.

Black sea bass is a perfect chowder fish. Flounder is nice when cut in fillets and served in a variety of different ways. Scup can be panfried or baked whole.

At 9:30 in the morning, Mr. Potter cranked up the boat radio with music from the band Boston: More Than a Feeling.

Mr. Devine was clearly happy about his fishing efforts: he had caught more fish than he had drunk from his private stash of beer. “I like the fish to beer ratio,” he said.

He wasn’t the only beer lover aboard.

Chris Vreeland, 31, of Otisville, N.Y., sells beer for a living and had brought a small cooler loaded with samples. He shared with his fishing buddy Thad Izzo, 38, of Northville, N.Y.

Mr. Vreeland caught a fish and started reeling it in. “Over the rail and into the pail,” said Mr. Smidt.

Mr. Vreeland pulled in a large black sea bass.

Nearby, a black-backed gull watched closely. “Billy,” declared Mr. Potter. “Billy is always with us. He meets me in the morning.”

Mr. Smidt looked at Mr. Vreeland’s fish and voiced his approval.

When the Skipper stopped at a new spot, Mr. Potter yelled out to his audience: “Go get ‘em.”

The music on the boat sound system changed to Jimmy Buffett. Anglers were reeling in sizeable black sea bass and the morning was still young. Everyone aboard had caught at least one fish.

Minutes before the charter was over, someone was onto another fish. The six-foot rod bent over. Anglers cleared the stern while he reeled in the fish.

It was the biggest fish of the trip, a six-pound bluefish. Once the netted fish was aboard, there was applause.