When the St. Regis Longboat Key opened last August, guests expected to find ultra-luxury Gulf-front guest rooms, pools, restaurants and spa treatments—all hallmarks of the storied hotel brand, which was founded in 1904 by John Jacob Astor IV, a wealthy businessman whose wife, Caroline, often visited Sarasota.

But they might not have planned on being able to swim with enormous Southern stingrays; to snorkel with 3,000 marine animals including lobsters, grunts, puffer fish and tarpon in a 500,000-gallon lagoon; or to hand-feed playful cownose rays, all within the confines of the 18-acre resort complex in the middle of Longboat Key, where The Colony Beach & Tennis Resort once stood.

In addition to its usual staff, the St. Regis Longboat Key also employs marine biologists, or “aquarists,” who lead the resort’s “Under the Sea Lagoon Experience.” They can ably answer participants’ questions, from whether or not the rays can sting them (no, their barbs are trimmed) to what kind of water the fish swim in (saltwater; the lagoon’s salinity is adjusted as needed). They also make sure everyone is properly outfitted with a life vest and snorkeling gear.

Biologists take visitors on three adventures. The first activity is feeding the cownose rays. Elizabeth German, one of the St. Regis aquarists, leads guests into the lagoon, which is blanketed in soft sand to mimic the ocean floor. Almost immediately, curious fish and rays begin circling. They know exactly what time it is.

German tucks four or five small fish, about the size of sardines, into guests’ gloved hands, instructing them to hold the fish like an ice cream cone and make sure their thumbs are tucked in so their digits aren’t mistaken for food. The cownose rays glide by and suck up the fish (their mouths are located on their underbellies). Swish! The treat is gone in a flash. The cownose rays, thrilled to be eating lunch, splash and flap their triangular wings against everyone’s bodies. They’re almost like puppies: cute, playful and demanding.

Meanwhile, the larger Southern stingrays—who know they’ll be fed soon, too—and curious fish flit from side to side, hoping that someone will drop some snacks. A wide-eyed, polka-dotted puffer fish named Alvin, one of three in the lagoon, is extra cute and friendly, sidling up like he deserves a treat, too.

Next up: Snorkeling in the middle of the lagoon, which deepens to 7 feet. Guests are handed a snorkel and float so they can glide facedown through the water to get a clear look at the fish darting back and forth below. In addition to the rays and puffer fish, there are lobsters, hogfish, lookdowns, angelfish, grunts, tarpon, yellowtail snapper, parrotfish and more—all native to the southern Gulf. It’s a riot of color and motion, especially with the bright midday sun creating golden criss-cross patterns on the lagoon floor.

The experience wraps up at the other end of the lagoon when German feeds the larger Southern stingrays. Today’s meal is big chunks of raw pink squid, and the rays have no qualms about the fact that humans have taken a seat in the middle of their dinner table. They glide over and around the guests, who stroke their velvety backs and squeal when they feel the rays’ bony tails brush against them.

The St. Regis is home to nine Southern stingrays, all female, each with her own distinct personality. One ray is extremely timid and skittish; another, Nova—the youngest of the group—is curious and playful. Rays are also picky about what they eat—not all of them like squid, for example. German and Dylan Scheaffer, another St. Regis aquarist, take careful notes about which ray eats what, so they can ensure all the rays are getting proper nutrition. There’s a different kind of fish provided at each feeding to ensure finicky rays will eat next time, German explains. And if a medical issue arises, the St. Regis works with an on-call veterinarian who specializes in marine life.

After the Southern rays are fed, guests wade out of the lagoon and shower off the salt and sand. A saltwater lagoon in a St. Regis hotel in Sarasota—what would John Jacob and Caroline Astor think? Odds are, they’d jump right in with everyone else.

Meet the Rays

Cownose rays

These playful rays are smaller in size, with brown backs, white bellies, triangular “wings” and rounded noses. They have teeth like tiles, which make short work of crushing crustaceans, mollusks and small fish. They swim in large, graceful groups close to the surface of the shallow, brackish water they prefer.

Southern stingrays

These large rays have a diamond-shaped body with dark backs and white bellies. Unlike cownose rays, which swim close to the surface of the water, Southern stingrays prefer swimming along the sandy sea floor and bury themselves in sediment to avoid predators. They can grow to 5 feet wide and weigh more than 200 lbs.

Did you know?

A group of rays is called a fever.

The Under the Sea Lagoon Experience starts at $149 per person and based on availability; participants are capped to keep groups small, and the experience is not included in hotel guests’ stay. For more information and to sign up, visit marriott.com or call (941) 231-1000.