This is an artist's impression of the world's deepest and largest (by volume) pool. It's a planned facility that could be used by astronauts to mimic the environment of space.
UK company Blue Abyss wants to build the 50-metre-long, 50-metre-deep pool at Essex University's "Knowledge Gateway" site in Colchester. The idea is that could be used by astronauts in training as well as divers and marine researchers of all varieties.
John Vickers, managing director of Blue Abyss, said it could even be "the world's first commercial astronaut training centre," offering would-be astronauts and space tourists a taste of the kind of weightlessness and isolation one usually has by leaving Earth.
But for someone aiming to build the world's biggest pool, Vickers explained that size isn't everything when it comes to space training. "To all intents and purposes, big is not necessarily better," he told me in a phone interview. "Depth is irrelevant—the only reason NASA's pool is 12 metres deep is to fit in various models of the ISS replica that they've got."
NASA's Neutral Buoyancy Laboratory contains full-size mock-ups of the International Space Station for astronauts to train with.
While exact depth might not mean much, the pool can be used to simulate the microgravity of space (it's not exactly the same, but it's good training). Vickers added that the planned pool has some other features geared toward space training.
"Round the peripheral edge of the pool we are creating a hyperbaric and hypobaric suite," he said. These mimic the increased and reduced pressures astronauts might experience if they're going out on a spacewalk, for instance. A room that would have a harness to mimic reduced weight outside of the water is also planned.
The pool also offers the kind of practical and psychological isolation you can't simulate in air: Being stuck in an environment where you're dependent on an oxygen tank and unable to immediately leave. "Especially obviously with a view to the future for Moon and Mars missions, extended periods of isolation with very few people round you, in an environment where you can't just open the door and say, 'I've had enough,' helps prepare," Vickers said.
He imagines this could be useful to commercial space travellers—a pool is admittedly a more pleasant training ground than a parabolic flight.
The pool is also aimed at researchers who might want to test remote-operated vehicles or other marine robots, and all kinds of divers.
The main advantage is that it's a controlled environment. But while it's not trying to recreate a real ocean, it's also not trying to be a big bath, with water temperatures around 19-23 Celsius and variable lighting and currents.
For now, the pool only exists on paper. Vickers said that Blue Abyss is working with architects and having discussions about finance with a number of sources, and plans to submit its planning application next month.
In the meantime, the project already has the support of UK astronaut Tim Peake, who said in a statement that he "supports Blue Abyss and sees this future facility as something that does not yet exist in Europe and that would compete with, or potentially even surpass, what is available in the United States and Russia."