Giant speakers thump out club hits as the DJ bellows: "Everybody get on the dance floor!"
The nightspot is a boarded-up swimming pool on a ship sailing in North Korean waters, and the groovers are mainly middle-aged men and women wearing pins featuring pictures of late North Korean leaders Kim Il Sung and Kim Jong Il.
Conspicuously missing is the beat of South Korean pop star Psy's Gangnam Style. "We're not allowed to play that one," explains Mr Danny Tay, the 46-year-old Singaporean who owns the ship.
His Royale Star is the only ship permitted to ply North Korea's first commercial cruise route running between north-eastern Rajin port and the scenic south-eastern Mount Kumgang resort. Since getting its licence in February, it has made three trips. Formerly a gaming ship in Singapore waters, the 138m-long vessel is no luxury liner, but a big improvement on the previous ship approved to ply the same route, the Mangyongbyong, with its bare minimum of amenities.
The Royale Star's bathrooms are functional, for starters, and all passenger cabins on its nine decks come with bunks, allowing for up to 250 passengers, with room for 250 crew. There are also a karaoke lounge, a duty-free shop, a small casino, a massage parlour, and a hair and nail salon.
The Pyongyang government representative overseeing operations on board told The Sunday Times: "Customers seem happier with the Royale Star than with the ship before, so our government is pleased with its crew and Singaporean management... This cruise is important to developing our tourism, and we want to give more people a taste of North Korea."
So how did a Singaporean and his modest vessel end up promoting tourism in reclusive North Korea? Mr Tay says he made the first move last year after learning that North Korea had a cruise route.
A primary school dropout who worked his way up the marine industry and who acquired the Royale Star in 2011 under his British Virgin Islands-registered company, Everis Capital Holdings, he approached North Korean officials to pitch his idea and the deal was sealed at the end of last year.
"It's been a dream to venture into North Korea since I was sent to repair a ship's elevators in North Korean waters back in 1996," said Mr Tay. "I don't speak the language but saw an opportunity and the untapped potential in cruises there."
The cruise is being marketed as a way for foreigners to visit one of the world's most secretive countries, and several passengers on board during its latest trip at the end of last month told The Sunday Times that curiosity had indeed prompted their travels.
"This country is very mysterious because it's so closed to the outside world, and I've always wanted to see what it is actually like," said Jalan Besar nasi lemak hawker Ng Chue Hiang, 54, the lone Singaporean passenger. "I heard about the cruise from a friend who said the scenery is fantastic, so I decided to give it a try, as I don't think there will be many chances in life to travel to North Korea."
The five-day, four-night 4,000 yuan (S$828) cruise is targeted mainly at foreigners, and most so far have been from China. Those who want to join the cruise must approach the vessel's management directly, or sign up at the Royale Star booth in Rajin port.
The cruise is still in its trial stage, said Mr Tay, who hopes his floating hotel and casino will be allowed to run two trips a month. "This cruise is a challenge. Whether or not it will take off, we will see, but it's a risk worth taking and it's been a very exciting journey so far."