Airbnb is offering a free, two-night stay aboard the research vessel Alucia, coupled with an underwater dive on a submarine. All you have to do in order to spend April 5th–7th out at sea off of Cape Eleuthera in the Bahamas, is enter and win a competition. Contestants have to submit a 50- to 550-character essay about “what you dream of exploring beneath the waves.”

The Alucia is an 184-foot exploration vessel designed to conduct scientific research out in the ocean. The ship was used in the filming of Blue Planet II, the BBC documentary about the world’s oceans that premiered in the US on January 20th. In fact, Orla Doherty, one of the show’s producers, will be the host of the Airbnb contest, greeting winners on the vessel and telling them all about her own adventures diving over 500 hours beneath the surface. There are just a few “house rules” for the guests: no skinny dipping, no sleepwalking or night swimming, no fishing, no selfies with the deep sea creatures, and no high heels. (“This is a research vessel, not a cruise ship.”)

The trip, which runs in full from April 4th to the 8th, includes an underwater expedition aboard one of the Alucia’s two submersibles, the TRITON 3300/3 or the Deep Rover. The subs are designed to withstand hundreds of pounds of pressure to conduct marine science research, explore shipwrecks, and take underwater videos. “Along the way you are sure to see a magical menagerie of underwater creatures,” the Airbnb post says.

This is not the first time Airbnb is offering free stays in unusual locations. In 2016, the company let two people sleep in an underwater bedroom surrounded by 35 sharks in the Aquarium de Paris. In that case, people also had to submit an essay to win a spot in the circular room. (The shark tank room had no bathroom and couldn’t host guests weighing more than 419 pounds together.)

This latest competition is open to people 18 or older who are in good physical health from the following countries only: US, Canada (excluding Quebec), China, Singapore, Philippines, Taiwan, Hong Kong, Indonesia, Malaysia, Germany, Portugal, Spain, and the UK. Three people will be chosen based on how good their essays are, and each will be able to bring one guest along on the trip.

You have until February 10th at 7AM ET to enter the contest — and do so at your own risk. Diving deep into the dark ocean takes some courage: Doherty’s own yellow submarine started taking on water on her first dive into the frigid waters of Antarctica. The leak was fixed within 20 minutes — but still, that’s not exactly the sort of thrill many people would seek on a trip to the Bahamas.