Big banks deserted Wall Street. Then the cool kids moved in.

But long gone are the days of underwriters and accountants. Today, the building is a stylish creative mecca, filled with chic decor and amenities fitting a luxury resort.

If you’re among the designers, artists and founders who work in what is now called the Water Street Associates building, your first coffee or matcha is free before 11 a.m. On certain floors, a stainless steel refreshment cart makes the rounds twice a day, offering complimentary tea and fruit in the mornings and oysters and truffles in the late afternoon. On Thursdays and Fridays, there’s champagne. An in-house florist creates sculptural arrangements for the building, and amber, sandalwood and orange blossom scents waft through the halls. Several floors have a concierge to help with everything from scheduling a meeting room to sending out dry cleaning. Oh, and some of the rents are below market rate (for now).

The building springs from the vision of a trio of investors looking to revitalize the area: Matthew Khalil, Carlo Bellini and Dawson Stellberger. To bring it to life, they hired Matthew’s wife, Gabriella Khalil, as creative director. A hospitality doyenne best known for the celebrity-studded, widely Instagrammed Grand Cayman resort Palm Heights, she oversees WSA’s design and programming while the others handle the real estate. The goal of the project is to help creative people build a professional community.

“I do feel like the office is back," Gabriella says. “It feels like people want to come to work, they feel good about it."

Though the U.S. office market is in meltdown mode with soaring vacancy rates, you wouldn’t know it at WSA. The leasing office has filled the building without ever putting up a listing. All of the tenants have come from word-of-mouth; many of them know the Khalils from staying at or collaborating with Palm Heights. There’s even a wait list.

Current tenants include fashion brands like Rosie Assoulin, Luar and Bode, which has the entire 11th floor; the culinary collective Ghetto Gastro; Sue Chan and her event marketing agency, Care of Chan; consumer brands like nonalcoholic drink company Ghia; and many more.

In addition to office spaces, WSA offers spa services on its 23rd floor, called the Water Lounge. These include facials, lymphatic drainage and exercise classes. There’s a residency kitchen on the 15th floor that has hosted the L.A. restaurant Gjelina. The 10th floor is an executive lounge, where founders and directors can take private calls and meetings, or just visit to sit and think. (They can also bring their teams there.) In the event space on the 16th floor, GQ hosted its Creativity Awards this year. There are recording studios for podcasts, photo studios for shoots, gallery spaces and rooms for seminars and classes.

Other commercial landlords in Manhattan are offering deal sweeteners to attract tenants, including about a month of free rent a year and allowances to make improvements to their spaces. Manhattan’s office availability rate was 17.9% at the end of June, down slightly from an 18.1% all-time-high recorded in the first quarter. And while some areas including Midtown and Hudson Yards are starting to see improvement, downtown and the financial district are facing higher availability rates (20.4% and 25.4%) than the city average. The average rent per square foot in downtown Manhattan is $57.08 compared with the borough’s overall $74.26 average, according to data from real-estate consulting firm Colliers.

AIG moved its headquarters to Midtown in 2020, and 161 Water Street sat mostly vacant for a couple of years before Matthew, along with his partners, clocked its potential. Through representatives, he declined to be interviewed. Though he likes to be behind-the-scenes, Matthew is a successful real-estate developer whose true passion is said to be the arts. The real-estate firm Matthew co-founded, Khalil & Kane, is based in London. WSA is owned by WSA Waterfront LLC and 99c LLC, which is led by Bellini, a Canadian biotech entrepreneur; Matthew is a principal, as is Stellberger, a real-estate developer. Also in 99c LLC’s portfolio is a members’ club in Brooklyn called Scott Avenue Associates with a bustling rooftop restaurant; SAA has also hosted events, including a Luar runway show attended by Beyoncé.

After Gabriella visited the WSA building for the first time, she knew she wanted to play with its ’80s bones. Many of the floors feel like a Wall Street-inspired wonderland, with wall-to-wall carpeting, modular metal cubicles, vases of calla lilies, stainless steel reception desks and potted plants everywhere—all of which have made a nice background for a number of fashion shoots.

“A big part of this is approaching it from a hospitality perspective, little details that make a difference in your daily life," Gabriella said. “What’s the equivalent of a turndown service that we would do at a hotel?"

Many other floors and amenities are on the way, including a canteen for casual lunches, a restaurant filled with velvet, olive-colored seating, a screening room and a state-of-the-art recording studio. There will be a gym with a boxing ring and a spa with a hammam, sauna and cold plunge. There are plans for a colossal retail space that will sell products from the brands that work in WSA.

Right now, some of WSA’s tenants say they are paying unusually low rent, thanks to a $41 million city tax break the building owners received as part of the Manhattan Commercial Revitalization (M-CORE) project. The building’s goal is to bring new, creative tenants to the area and foster the creation of jobs. For M-CORE tenants, rent steadily increases over time, usually reaching market rate around year three. A representative for the building said that lease terms are confidential.

“We’re very transparent about where the leases are going, we lay out the path for people," said Sam Wessner, who oversees special projects for the building. “We’re following traditional market terms for a lease, meaning leases do increase over the lease term. Each individual has to make the assessment of whether they can afford this."

Representatives for the building declined to say when they expect it to reach profitability. Every tenant interviewed said they’d like to stay in the building in the long-term.

Kevin McIntosh Jr., the founder of the communications company KMJR. World, was the first tenant inside WSA. He’d been going to Palm Heights since it opened in 2019 and moved into WSA last June when his prior office lease was up, before construction was complete.

“I saw what the team did with Palm Heights," said McIntosh. “I was never worried." He signed a four-year lease.

Working in the building has led to professional opportunities for tenants including McIntosh, who did the PR for Bode’s recent collaboration with Nike. Often “when brands or people talk about ecosystems and community, they’re forcing something," he said. “When you come in here, it’s the real s—." McIntosh, who recently bought an apartment nearby WSA, also produced a Met Gala afterparty on the building’s 28th floor with co-hosts that included the models Emily Ratajkowski and Paloma Elsesser.

When Neada Deters, the founder of skin-care brand Lesse, moved her team of three into WSA earlier this year, she pictured herself going in four days a week. But, by choice, she and her employees have found themselves in the office Monday through Friday, every week. One of her favorite parts of working in the building is that it feels like she runs into people she knows there every day.

Henry Ellis, chief product and innovation officer of nonalcoholic aperitif brand Ghia, tried WeWork using a free membership. “I was like, this is not for me," he said. The L.A.-based company moved its smaller New York team into a four-person office at WSA at the end of 2023 and hasn’t looked back. “You feel taken care of here," Ellis said.

Fashion designer Rosie Assoulin moved her showroom and offices from Soho to the WSA building a few months ago and is making herself at home. “I wish I could have a pullout bed and a few extra bedrooms for my kids," she said.

With most banks gone from the neighborhood, Gabriella said that she would love to bring new energy to FiDi and the Seaport. “There’s this trickle effect when you see people around and then hopefully, as things progress with the retail space, there will be even more that we can really offer within this area," she said. Many tenants interviewed said they enjoy eating at Jean-Georges Vongerichten’s nearby Tin Building, but other than that, most go to surrounding downtown neighborhoods like Chinatown, Tribeca and Soho for an after-work drink or meal.

Celebrity facialist Cynthia Rivas had a studio on the Upper East Side when the WSA building’s Water Lounge presented an opportunity to expand into a bigger space. There, she’ll eventually train other facialists to work under her and launch a members’ club. She called the 23rd floor a one-stop shop for clients, where they can book appointments for hair, nails, brows and more—a rarity in the costly commercial market of Manhattan.

“Sometimes," she said, “it doesn’t even feel like I’m in New York."

Write to Lane Florsheim at lane.florsheim@wsj.com