The world's deepest diving pool has opened, complete with artificial underwater caves and Mayan ruins, in Poland.
The complex, Deepspot, even has a small wreck for scuba and free divers to explore.
The 45.5-metre-deep diving pool opened near Warsaw this weekend.
It has 8,000 cubic metres of water – more than 20 times the amount in an ordinary 25-metre pool.
Unlike regular swimming pools, Deepspot can open despite coronavirus restrictions because it is a training centre that offers courses.
A hotel with rooms from which guests will be able to watch divers is also planned.
"It's the world's deepest pool," said Deepspot director Michal Braszczynski, 47, a diving enthusiast.
The holder of the Guinness world record for the deepest dive pool is Montegrotto Terme in Italy, at 42 metres.
The Blue Abyss pool, which is planned to open in Britain in 2021, will be 50 metres deep.
About a dozen customers visited on the first day at Deepspot, including eight seasoned divers who hoped to pass an exam to become instructors.
"There are no magnificent fish or coral reefs here so it is no substitute for the sea, but it is definitely a good place to learn and to train in order to dive safely in open water," said Przemyslaw Kacprzak, 39, an instructor.
"And it's fun. It's like a kindergarten for divers."
Jerzy Nowacki, 30, a forestry officer and diving novice, said: "For my first time, we went down five metres but you can see all the way to the bottom – the wreck, the caves. It's magnificent."
Mr Braszczynski said the pool would also be used by the fire brigade and the army to train.
"There are many scenarios for training and we can also test different equipment," he said.
About 5,000 cubic metres of concrete were used over the two years it took to build the pool, which cost about $10.6 million.