By Michele Parente

Summer at San Diego-area casino resorts unofficially kicks off today with the opening of Pala Casino Spa & Resort’s new, adults-only pool complex.

The Tourmaline Pools, part of Pala’s $170 million expansion, features five pools surrounded by 14 luxury cabanas, two oversized hot tubs, a poolside bar and restaurant and a lounge area with fire pits.

Pala is the latest area casino to unveil what’s become a must-have destination amenity — a splashy, Las Vegas-style upscale pool area.

Whether kid-friendly or 21-and-over, these aquatic playgrounds have everything from water slides and splash pads to lazy rivers and swim-up bars, in-water lounge chair Baja shelves, fountains, waterfalls, spas, day beds and swanky, fully equipped private cabanas.

“The U.S. casino industry has grown immensely over the past two decades and a large part of that growth is attributable to casino operators responding to the demands of their clientele for a broader range of recreational activities for them to enjoy when visiting a casino resort,” said Pala CEO Bill Bembenek.

“Pala realized very early on that our diverse clientele are equally as diverse in how they define a quality recreational experience,” Bembenek added. “Thus, we have consistently added resort amenities to our casino such as our Four-Diamond hotel and spa, 10 restaurants, our wine cave, several bars and lounges, multiple concert venues and most recently Tourmaline, Pala’s new adults-only pool experience.”

To accommodate expected demand, Pala today also unveiled its renovated hotel parking garage, with 420 additional spaces. And it’s weeks away from the June 29 opening of a new 15,000-square-foot, glass-enclosed non-smoking casino area as well as an expanded main casino floor, by 10,000 square feet, and its centerpiece Marquise Bar.

But a lot of the action at casinos this summer will be happening outside.

Earlier this year, Pechanga Resort & Casino and Viejas Casino & Resort debuted new pool areas that were part of larger expansion projects that added an additional hotel tower at each property.

Pechanga’s out-sized, $300 million expansion came with an equally extensive, 4½-acre pool complex called The Cove. It has three pools, including an infinity-edge main pool with a swim-up bar, Baja shelf and waterside day beds. A family pool sports two waterslides and a splash pad. Five spas, 27 cabanas and The Coveside Grill restaurant and bar round out the amenities.

“The one and only oversight we made in the original resort was not building a spectacular pool,” said Edith Atwood, president of the Pechanga Development Corporation.

“With this $300 million expansion, we set out to make a statement with our new pool, The Cove, that exceeds Southern California experiences. The comments we’ve received so far tell us guests love it.”

Viejas, meanwhile, went a more exclusive route, adding Allure, an adults-only saltwater pool that’s for the sole use of guests staying at the new resort-within-a-resort, Willows Hotel & Spa . Surrounded by a new tranquility garden, the Allure pool was designed to provide a genteel, grown-up experience.

Meanwhile, construction continues at Sycuan Casino , which is building its first hotel — a 300-room, 12-story tower with a spa and fitness center — and an 8-acre pool complex.

Sycuan’s pool and gardens area will have a resort-style adult pool, with cabanas and a bar and grill, as well as dedicated family pool and a lazy river — a water park favorite that allows you to float along it by a gentle current.

The only other lazy river at a San Diego-area casino resort can be found at Harrah’s Resort Southern California . Harrah’s was the first to open a sizable, Las Vegas-style resort pool with multiple amenities. Its complex has a 21-and-over main pool, with spas, cabanas, palapas, day beds and fire pits, a tropical swim-up bar and lounge area, and a lazy river with coves and waterfalls.

In the past few years, an estimated $1 billion has gone toward casino development projects in the region, bringing new hotel towers — Pala will open its second tower in 2019 — luxury spas, trendy restaurants, increased gaming space, and of course, new pool complexes.