The bachelorette party made its way toward the entrance of Seacrets, the young women sporting tank tops with such mantras as: “I need a break from class, put some wine in my glass” and “I’m here to party, buy me Bacardi.”

It was their first night in Ocean City, the first night of a girls’ weekend to celebrate a friend’s upcoming wedding. Most of them grew up near Olney, so this was the beach where they vacationed as kids. And this was the bar they frequented during college breaks.

Well, bars. Seacrets is an “entertainment complex” spanning six acres and featuring 18 drinking establishments, a radio station and a hotel — a good-times empire built by an Ocean City native who dropped out of high school at 16.

Each weekend between Memorial Day and Labor Day, more than 25,000 people wait in line to get inside. On holiday weekends, that number can surge to more than 50,000, making it one of the busiest, highest-grossing bars in the country.

Most customers have been to Seacrets before and will return, part of a beach economy built on ritual. In this town, the surf, sun and sand have to be accompanied by doughnuts at the Fractured Prune, french fries at Thrasher’s, crab cakes at Phillips and, of course, a boozy night at Seacrets.

“Noooo!” one bachelorette whined when she saw the long, snaking line separating their party from partying just after 11 on a Friday night. Another wondered aloud: “Why is there a line? It’s not that late.”

The burst of unhappiness caught the attention of a bouncer, who led the women to another entrance. One by one, they presented their IDs, walked through a metal detector, opened their purses for guards to peek inside and paid a $10 cover.

Then they walked up a sandy incline as a cool August breeze blew their hair back from their faces. To their left was a nightclub with a cover band playing pop hits. To their right, a DJ blasting a song about booty calls. Before them was an old boat that has been converted into a bar and restaurant, sheltered under a grove of palm trees imported from Florida. Beyond that was Assawoman Bay, quietly reflecting the resort’s brightly colored lights.

“I like the sand,” declared Molly Lethbridge, the 25-year-old bride, prompting some mocking from her bridesmaids and friends. “I do! It’s like you are on the beach all night long.”

That’s part of the secret to Seacrets’ success and what has transformed it from a simple tiki bar to a sprawling resort that can hold 4,600 people at a time.

Staffers at Seacrets wouldn’t divulge how much revenue the complex generates. But Technomic Inc., an industry research and consulting firm, estimates the megabar raked in between $15 million and $25 million in 2011. That put Seacrets at No. 15 on the Nightclub & Bar Top 100, a list of the highest-grossing venues in the nation. (The list is dominated by Las Vegas hot spots, but three D.C. clubs made the cut: the W Hotel’s P.O.V. at No. 44, LOVE at No. 63, and the Park at 14th at No. 85.)

Nearly all of Seacrets’ money is made during the summer. The busiest weekend of the year is also the first of the season: Memorial Day weekend, when 50,000 to 60,000 guests are served by more than 500 mostly new bartenders, waitresses, hostesses and other employees.

“Memorial Day is like trying to play the Super Bowl without practicing,” said Rico Rossi, a Seacrets general manager who started as a bartender at the original tiki bar in 1988. Business will tail off dramatically after Labor Day weekend.

In between, Seacrets is open almost continuously, closing at 2 a.m. and sending mobs of 20-somethings swarming the Coastal Highway. The place reopens at 8 a.m. for breakfast, which is especially popular with gray-haired retirees who might otherwise never step foot inside.

During the day, the most coveted seats are in the bay — half-submerged stools and tables and floating rafts. People start lining up hours before the tables open at 11 a.m., and they stay until they are kicked out of the water at dusk. Music blares, cellphones are ruined and waitresses in bikinis collect hundreds in soggy tips.

“The sun is shining, you’re having too much fun, you’re drinking a Corona. . . . It’s almost like you’re somewhere else,” explained Brigitte Ferraz, 22, a babysitter from New Jersey who has been to Seacrets five times this summer, each time arriving around noon and leaving after midnight.

“I am loving Seacrets.”

The creator of this sprawling resort, Leighton Moore, grew up in Ocean City and learned about the hospitality business from his parents, who ran a hotel just a block from where Seacrets now rises from the sand.

By his own admission, Moore wasn’t the greatest student. He got his GED when he was 16 and then hopped on a plane to Jamaica with a friend. The two arrived in Montego Bay with hardly any money and took a bus to Negril.

“And I fell in love,” said Moore, now 60.

Moore absorbed not just the island’s vibe but also its beach business model, taking note of its shacklike bars that sometimes morphed into restaurants or even resorts. Those lessons would eventually be put to use in the creation of Seacrets, which opened in June 1988 as a modest private club that catered to locals.

The tiki bar became wildly popular, and Moore began adding to it. He bought up parcels of land, including condo buildings that he purchased unit by unit.

The goal was for Seacrets to look, feel, smell and sound like Jamaica. Each spring, more than 20 trucks arrive in Ocean City carrying 375 palm trees from a plantation in Florida. It takes a crew with a crane nearly two weeks to uproot the dead trees from the previous summer and plant a fresh batch. The crews also place 4,500 tropical plants in the Maryland sand.

“They’re going to die. I want them to die, because that way I am the only jungle in town,” Moore says. “If I am going to charge six, seven, eight dollars for a drink, people want real trees.”

Despite the palm trees and the 45,000 pounds of jerk chicken served each summer, Seacrets is not always a paradise.

The recession forced the complex to scale back from 21 bars to 18. And there have been a few incidents that have marred its history.

In August 1990, a New Jersey father dived off a deck at Seacrets late one night after hours of drinking, breaking his neck and later dying. His family sued, but a judge ruled in 1995 that Seacrets was not responsible for his death.

The resort is in the midst of another lawsuit brought by a Pennsylvania woman, who was brutally raped near Seacrets during Memorial Day weekend in 2008 after she was kicked out for being too drunk to walk properly. A Florida man recently pleaded guilty to the rape in Worcester County Circuit Court and is serving a 30-year sentence. The woman has sued Seacrets, claiming that it didn’t do enough to protect her that night, which in court papers the company denies.

Although most locals express appreciation for Moore’s charitable donations, people with homes along the bay have long complained about the noise that travels across the water. To muffle the cacophony, sound barriers have been installed, and the loudest parts of the complex are put as far from the water as possible.

Moore no longer runs Seacrets day to day. For five years, he has relied on his longtime employees to manage the operation.

Now he’s devoting his attention to building boats. He was awarded a contract by Ocean City municipal officials to construct a flat-bottomed fireboat that can travel in water that’s only six inches deep.

Even so, Moore is looking to expand Seacrets again.

There are plans to build a much nicer, full-service hotel and banquet facility. And he talks about launching a second Seacrets in Florida, the Virgin Islands or Mexico. He thinks it will be easy to replicate the resort if he can just find the right spot.

“It’s time to move,” Moore said. “Time to move somewhere new. Take the show on the road, maybe to where palm trees live.”

Inside the dance club at Seacrets on a Friday night, hundreds of people are grooving to a cover band’s rendition of Fun’s “We Are Young.” It’s too loud to hear a cellphone ring or to communicate in any way but text message.

“Tonight! We are young!” the leader singer belts as the mob on the dance floor jumps in unison, beer splashing out of Miller Lite and Red Stripe cans. “So let’s set the world on fire.”

Midnight hits. Colorful balloons and confetti fall from the sky as if it were New Year’s Eve — a nightly ritual at Seacrets.

Two hours later, the music stops, the lights come on and the sweaty horde is ushered toward the exits. The crowd makes its way to a cabstand or out to the highway to wait for the “drunk bus.” There’s singing and shouting, kissing and hugging, and posses organized for late-night food forays.

The same scene will unfold every night at Seacrets until fall arrives.

“Beginning and ending the summer at seacrets,” tweets one college junior at 2:29 a.m. “i can’t believe it ended so fast.”