(CNN) — Ever wanted to sleep amongst manta rays inside the world's largest aquarium? How about unwinding in a floating sauna in a Swedish archipelago of 10,000 islands?
As hotels compete to create ever more awe-inspiring and Instagram-worthy spaces, some architects are turning their engineering focus to building on water. Situated in prime locations around the world, these nine floating hotels are either permanently docked on water, wholly mobile or partly submerged below sea level and make a most interesting place to stay:
1. Taj Lake Palace, Udaipur, India
Taj Lake Palace: As loved by Roger Moore-era James Bond.
Courtesy Taj Lake Palace
Floating like a huge spectral white mansion in the middle of an Indian lake, it's easy to see why this palace was chosen as a backdrop for the 1983 James Bond film "Octopussy."
Its history is as seductive as the sights it offers. Prince Maharana Jagat Singh II built the hotel in 1746 as a pleasure palace, legend has it, for hosting his dalliances with beautiful young women. It was restored to its opulent former glory in the 1970s.
Guests are greeted with champagne as they arrive via private jetty, while attendants wait with embroidered umbrellas to escort them indoors. There are 66 rooms and 17 suites, all with views of the lake.
Inside, there are plush pillow-strewn sofas, along with exotic paintings, carved white marble terraces, a stunning courtyard and spa. Its chefs blend the ancient cooking techniques of royal cuisines with signature local dishes.
All that extravagance not enough? The hotel can arrange special sightseeing tours around Udaipur city in one of its effortlessly cool vintage cars, including a 1948 Jaguar.
Taj Lake Palace, Lake Pichola, 5 Udaipur, Rajasthan 313001, India; +91 (0) 294 242 8800
2. Manta Resort, Tanzania
Built on the little-known Pemba Island off Tanzania and Zanzibar's mainland, Manta Resort boasts many eye-popping details but none more breathtaking than its Underwater Room.
Designed by Swedish company Genberg Underwater Hotels, the room was seven years in the making and is a follow-up project to its Swedish hut-style Utter Inn, afloat on Sweden's Lake Malaren near Stockholm.
The watertight chamber floats some 250 meters off shore in a federally protected zone within the turquoise waters of the Indian Ocean.
There's a rooftop deck, a bathroom and a lounge area at sea level. Its showpiece -- a glass-walled bedroom submerged four meters (13 feet) underwater -- offers glorious views of more than 100 marine species.
"It's a very private experience, you are there on your own little island," says Manta's CEO Matthew Saus.
The structure naturally attracts fish and at night spotlights under the window illuminate squid and octopus as they climb onto its windows in search of food. Its astounding views of corals and Spanish dancer sea slugs are perfect for cashed-up romantics.
"We've had 10 engagements within the room -- all successful, I might add," beams Sauss. More submerged rooms were planned for 2018.
3. Good Hotel London, UK
Good Hotel London: "Pure design."
Courtesy Good Hotel London
Opened late in 2016, this 148-room hotel turns a former detention center for illegal immigrants into a lavish "floatel."
Good Hotel launched in Amsterdam in 2015, before journeying to the UK across the North Sea via the aide of a submerged barge.
It's taken up residence in London's Royal Victoria Docks, where it'll remain for the next five years. Aptly named, the hotel aims to do "good" by helping the long-term unemployed find jobs through a three-month traineeship.
Highlights include a rooftop terrace garden overlooking the river Thames. The room designs embrace modern ideas around simplicity and clean lines -- dark walls and solid raw-wood furniture are paired with fabrics in neutral tones.
"The design is very pure," says Good Group's marketing director Marie Julie Craeymeersch. "It's designed with an eye for detail but with local touches coming through textures."
Socially minded travelers will also be pleased to find all its food and beverages sourced locally.
Good Hotel London; Docklands Royal Victoria Dock, Western Gateway, London, England; +44 (0) 203 637 7401
4. Conrad Maldives
Ithaa: Conrad Maldives is home to the world's only all-glass underwater restaurant.
Suspended across two islands, and set on stilts above the Indian Ocean, Conrad Maldives' over water villas may just be the best in barefoot luxury.
Its Sunset Water Villas on Rangali Island are accessible only by jet boat or via a private walkway. Access to the main Rangalifinolhu Island is via a 500-meter bridge.
Each of Rangali's 50 villas features an infinity pool while indoors, you can view the clear blue waters below through glass flooring in the center of the living area.
In 2005, Conrad Maldives opened an all-glass underwater restaurant, named Ithaa, meaning Mother of Pearl.
Located 5 meters (16 feet) below sea level, its transparent roof and walls provide 180-degree views. An indulgent cuisine of caviar and Maldivian lobster await as manta rays, sharks, and turtles swim above you. The restaurant doubles as an underwater chapel for couples looking to exchange wedding vows.
5. Salt & Sill, Sweden
Salt & Sill: Bed to sea in under 10 seconds.
Courtesy Salt & Sill
Located in the Bohuslan Archipelago of around 10,000 islands, the Salt & Sill hotel drifts along Kladesholmen Island, its waters profuse with fish, and fondly referred to by locals as Herring Island.
Owners Sanna and Patrik Hermansson were looking to add rooms to their seafood restaurant but the island had no capacity. Instead they built six two-story buildings on pontoons in the waters of the Skagerrak.
"Sill" means herring in Swedish and the hotel specializes in serving it three ways alongside schnapps.
There are 23 bedrooms, in Scandinavian minimalist style, and some on the lower level have their own ladder leading straight into the sea.
"The marine life underneath the floating pontoons is a perfect habitat for shells and mussels," says owner Sanna Hermansson.
Another big draw is its man-made lobster reef measuring around 40 square meters and a catamaran hosting a floating sauna. The hotel also makes efforts towards sustainability, with a small part of the electricity here powered through the sea's strong currents.
Salt & Sill; 471 51 Klädesholmen, Tjörn, Sweden; +46 (0) 304 67 34 80
6. Beach Villa Ocean Suites at Resorts World Sentosa, Singapore
Beach Villas Ocean Suites: The best way to make friends with a ray.
Resorts World Sentosa
Not so much floating, but part-submerged along one side of Singapore's S.E.A. Aquarium, which lays claim to being the world's largest.
Resorts World Sentosa's outrageous experience affords you the luxury of "living under the sea" with over 50,000 marine animals for company.
There are 11 two-story suites laid out like townhouses. The upper level has the living area, and an outdoor area with a Jacuzzi. Its underwater level contains the bedroom with a sunken Jacuzzi bathtub and floor-to-ceiling acrylic paneling looking right into the aquarium's man-made Open Ocean habitat.
Guests can recline in bed as the sea's gentle giants, including manta rays and leopard sharks, calmly swim past.
Despite being submerged, the suites still come with all the amenities you'd expect from five-star luxury including Wi-Fi, 24-hour in-room dining and 24-hour personal butler services.
7. Salt & Water Catamarans, Serbia
Salt & Water detachable catamarans: Choose your own adventure.
Courtesy Salt & Water
These mini "houseboat" type catamarans can accommodate two to four people with a bathroom, a hall with storage space and a bedroom above the living area.
They are being developed by Novi Sad-based design studio Salt & Water with the aim of promoting nautical vacation experiences that extend beyond the seaside.
"We saw a lot of inland water which [was] not always utilized or enjoyed and saw a lot of potential," says director Svetlana Mojić. "This is a solution that is designed for inland water. It's for lakes, channels and rivers."
Docked onto a central floating hotel with a reception and restaurant, each catamaran can be detached and navigated for a more private experience.
"It allows guests to choose the perfect location for a vacation on their own," adds Mojić.
In terms of functionality, the catamarans operate like any other boat but solar panels atop the roof add an eco-friendly touch.
Notching up a Millennium Yacht Design Award last year for the blueprints, physical catamarans go into production end of 2017.
8. OFF Paris Seine, France
OFF Paris Seine's Sunset Suite: Full blast of orange.
Courtesy OFF Paris Seine
Parisians are hard to beat when it comes to style, and this boat hotel on the River Seine is no exception.
Moored near Austerlitz station, OFF Paris Seine has some rather eclectic design elements -- a lounge ceiling covered with thousands of suspended metal sheets, luminescent bath tubs and basins, and a plunge pool bejeweled with a giant inflatable gold swan.
There are 54 rooms within the 80-meter-long hotel including four suites, split between the main and upper decks.
Its Sunset Suite is a wash of orange from walls to soft furnishings, all envisaged by trend forecaster Tal Lancman and haute couture designer Maurizio Galante.
On warm nights, guests can tuck into tapas and cocktails at the bar.
OFF Paris Seine; 20-22 Port d'Austerlitz, 75013 Paris, France; +33 (0) 1 44 06 62 65
9. Solent Forts, UK
Solent Forts: Built to withstand invasion, now welcoming visitors.
Courtesy Solent Forts
Solent Forts, off England's south coast, began life as three man-made sea fortresses commissioned in the mid-19th century to see off a French invasion that never materialized.
The fortresses were later used as military defenses during World War II but were abandoned by the 1960s. Now, two of the three fortresses have been turned into private vacation islands.
Guests pass through Solent's own departure lounge at Gunwharf Quays, before arriving by boat at either Spitbank, with eight bedroom suites and private hire, or the larger No Mans Land equipped with 22 bedrooms.
There are bars, restaurants, rooftop hot tubs and spas at both forts. Guests get champagne on arrival before being whisked off on a quick tour of the architecture.
While the communal areas of Spitbank are stamped with a playful nod to English naval history, its digs are a full jolt to modernity with chrome textures and glass paneling offering panoramic views of the sea. The original bolthole and lighthouse have also been kept intact.
To keep guests entertained on days when the English weather is unrelenting, there's a cabaret club, games room, and laser tag for those looking for '80s nostalgia.
From $1,206 (£1,000) per night, based on two people sharing, inclusive of meals and return boat transfers to Gun Wharf Quays.