Most hotels warn you about checking out late. At Jules' Undersea Lodge in Key Largo, Florida, checking out means strapping on a scuba tank, swimming up through a hole in the floor, and surfacing into daylight you haven't seen since yesterday. It's not exactly the Marriott experience - and that, of course, is the whole point.
Jules' holds a remarkable claim: it is the only underwater hotel on the planet where you sleep, eat, and wake up while submerged. Not a trendy overwater bungalow. Not a glass-paneled suite with a fish-tank floor. Actually, properly underwater, breathing compressed air in a repurposed research habitat bolted to the bed of a lagoon. The fish float past your bedroom window. A nurse shark has been known to nap on the doorstep.
The habitat sits at around 21 feet of depth, inside what is now the non-profit MarineLab Undersea Park. It sleeps up to six people and has been doing so, in various forms, since 1986. It is also the site of the world record for the longest uninterrupted stay in a fixed underwater habitat: 73 days, 2 hours, and 56 minutes. Biomedical researcher Joseph Dituri later pushed that record to 100 days in 2023. His girlfriend gave him a hard deadline.
America's First and Only Underwater Hotel
Jules' didn't start out as a hotel. Its origins are considerably more austere. The habitat began its life as La Chalupa, a scientific research station that operated off the coast of Puerto Rico from 1972. Built and run by marine scientist Ian Koblick and the Marine Resources Development Foundation, it was the largest and most technologically advanced underwater habitat of its era. For several years, teams of four or five scientists would descend for two-week missions, run their experiments, and surface when the work was done.
By 1976, the program had run its course. The habitat sat unused until 1980, when Koblick reacquired it, spent years refurbishing it, and reimagined it entirely. The idea: take the raw infrastructure of underwater habitation and open it up to anyone willing to learn to dive. By 1986, La Chalupa had a new name, a new home in a Key Largo lagoon, and a new identity as Jules' Undersea Lodge - named partly as a nod to Jules Verne, whose undersea visions had inspired generations of ocean explorers.
Jules' has since hosted scientists, celebrities, and curious civilians in roughly equal measure. Among its notable visitors: Aerosmith's Steven Tyler, actor Tim Allen, and former Canadian Prime Minister Pierre Trudeau. NASA-sponsored missions have also taken place here, including a 30-day program in which technology was developed that Koblick's team suggests may eventually surface in airports. La Chalupa was also, incidentally, the site of the first underwater computer chat session, hosted via an early online network called GEnie.
Getting In: The Moon Pool
Here's the part that stops most people cold: to get inside Jules', you have to be a certified scuba diver. There is no elevator, no pressurized tunnel, no clever engineering workaround. Entry is through what's called the moon pool, an open hatch in the wet room floor through which water and divers pass freely. You dive down, swim underneath the habitat, and pop up through the hole into breathable air.
If you've never dived before, the lodge offers a Discover Diving course that covers the basics and gets you comfortable enough for an escorted descent. It takes a couple of hours. You don't need years of experience to get down there - you just need enough competence to make the journey safely with a guide alongside you.
Before you submerge, a gear check and site orientation happen topside. You pack a bag - there are strict size limits, and anything you don't need should stay locked in your car. Your guide leads you on a dive of the surrounding Emerald Lagoon before escorting you down to the habitat. Phones can be brought down in sealed cases, which the staff will handle for you. Once you're through the moon pool and dripping in the wet room, the adventure proper begins.
The wet room itself sits between the two main sections of the habitat, housing the moon pool entry point, a shower, and a head. It's functional, compact, and perpetually damp. Think of it as the airlock between the underwater world and your temporary underwater home.
The Living Room, 21 Feet Down
The interior of Jules' is often compared to an RV - though an RV that happens to be fastened to the floor of a lagoon. The common room runs the width of the habitat on one side: a counter, a sink, a small refrigerator, a microwave, and a table with seating. It's not spacious, but it's fully functional.
There's a television. There's Wi-Fi - reportedly some of the best in the entire MarineLab compound, because when you're down there, you're the only person using the connection.
One adjustment you'll need to make: the air is denser than at the surface. At 21 feet of depth, you're breathing air compressed to about one and two-thirds of its surface volume. That means the effective oxygen concentration rises from around 20% to roughly 37%. Open flames are off the table as a result - no gas stoves, no hair dryers, nothing with a heating element. The microwave is your best friend. That, and the pizza delivery.
Yes, There Is Pizza Delivery
Jules' Undersea Lodge is, among other things, responsible for what may be the most inconvenienced pizza delivery route in human history. A dive-certified staff member suits up, takes a sealed waterproof container with a hot pizza inside, descends to the habitat, passes it through the moon pool, and hands it over for lunch. The lodge's manager has appeared in search results under the phrase "scuba diving pizza boy."
Pizza is the house specialty, but it's not the only option. Meals more broadly are included in overnight stays, and the kitchen can accommodate dietary restrictions and preferences. One group apparently received pasta primavera from a nearby restaurant, transported via the same sealed-box method. If you want it and it fits in a dry box, someone will probably bring it down to you.
The Bedrooms
On the other side of the wet room from the common area sit two sleeping cabins. Each contains a double bunk on the bottom and a single bunk above - the kind of arrangement that works fine once you've accepted that no one is staying for the thread count. The habitat can sleep up to six total, though the CO2 buildup from that many people breathing in a confined space is a genuine constraint, not just a house rule.
One documented quirk of long stays: people shrink. Biomedical researcher Joseph Dituri, who spent 100 days in the habitat, lost three-quarters of an inch of height due to spinal compression - the opposite of what happens to astronauts in low gravity.
He regained it after several months of hanging upside down once he surfaced. You're unlikely to notice anything after a single overnight stay, but it's a useful reminder that this environment, comfortable as it may feel, is not quite the surface world.
Each cabin has a large window looking out into the lagoon, and the common room has one too. The marine life outside doesn't behave the way it does when it knows divers are watching. Parrot fish drift past. Comb jellies feed in the light from the exterior lamps. Flatworms have been spotted cleaning the glass. A small sea spider was once photographed mid-dance on the window.
The staff keep an exterior light on at night near the common room window. It attracts plankton; the comb jellies follow. You can sit at the table and watch them open their bodies and envelop the food - a feeding behavior almost nobody ever gets to observe.
The World Record
In 2023, biomedical engineer and former naval diver Joseph Dituri descended into Jules' as part of a scientific mission he called Project Neptune 100. He stayed for 100 days, shattering the previous record of 73 days, 2 hours, and 56 minutes - itself a Jules' record, held by Bruce Cantrell and Jessica Fain.
Dituri's mission wasn't purely about endurance. He was studying the effects of long-term exposure to increased atmospheric pressure - about 70% higher than at the surface - on the human body. The results included increased collagen and stem cell production, doubled REM sleep, weight loss of 23 pounds, and a 100-point reduction in cholesterol. He cracked a tooth on day 12 and had to live with it for the remaining 88. His mother, who was in her eighties at the time, took a scuba lesson to come and visit him.
The potential applications of the data range from deep-sea research to future long-duration space missions. Whether or not you find that compelling, the image of a man being handed a bucket in a submarine while a nurse shark sleeps on his doorstep and a lobster molts outside his window is, by any measure, a remarkable one.
MarineLab
Jules' Undersea Lodge is now operated under the umbrella of MarineLab, a non-profit organization dedicated to marine science education. The Aquanaut program - which grants you the title of certified aquanaut after spending 24 continuous hours underwater - comes with a certificate and a story you'll be repeating for decades. The title dates to 1963, when man's undersea exploration was just getting underway and someone decided that people who lived underwater deserved their own word.
You can also pursue a PADI Aquanaut Specialty Certification as an add-on, though it isn't required for all members of a group. The lodge sells the experience as a bucket-list item for divers and non-divers alike - and the non-divers, arguably, are the more interesting category.
51 Shoreland Dr, Key Largo, FL 33037, United States
