In his musical treatise "Under the Sea," mononymous Jamaican crab singer Sebastian extolled the many benefits of life underwater. "Darling it's better," he assured us, "Down where it's wetter."

Gill-less humans can't sustain such a lifestyle, but a fantastical St. Cloud mansion known as Poseidon’s Fortress gets you pretty damn close. The five-bedroom, three-bathroom, 4,109-square-foot estate is a trip -- and that's by design.

"Each bedroom transports you to different areas of the world," reads the property listing for Poseidon's Fortress, which hit the market in May for $1.2 million.

Nestled next to the Mississippi River, the custom-designed space takes you from the ocean to the jungle, depending on the room. There's a tropical movie theater, a rock-cropped Aztec gym, a cave-themed bedroom, and an oceanic living room that transforms into a glowing dance floor. The 1.2-acre grounds feature a swimming pool sporting a mermaid paint job, plus a riverside guest house with 150 feet of shoreline.

A towering statue of the titular Poseidon -- Greek mythology's God of the Sea -- greets visitors in the front yard.

Listing agent Zach Duckworth describes the current owner as an eccentric medical professional with a fondness for world travel and rock music. Potential buyers view the home as one-of-a-kind, he reports, with some envisioning it as a B&B instead of a personal residence.

"If you say Poseidon House, people in St. Cloud know the property, and may know the owner," Duckworth says.

In the 2014 video posted below, the unidentified owner explains his inspiration for Poseidon’s Fortress.

"The vision and inspiration I had for this house came from my West Coast and desert life background, as well as my travels to the Pacific Coast of Mexico, to the resort area of Ixtapa-Zihuatanejo," he says. "The idea was to create my own little sanctuary here on the Mississippi River, a place that would transport my mind and spirit to the beautiful places of the world that I've visited, and to create a fantasy world where outdoor elements of beauty find themselves inside this house."

Built in 1958, the house was last sold in 1998 for $191,000, according to country records. The current owner is listed as RHI LLC.

Dive into these photos of Poseidon’s Fortress:

All photos courtesy of Team Lucky Duck/Keller Williams Preferred Realty; click here to view the property listing.