Underwater survival title Subnautica has shifted five million copies.

That's according to the founder of developer Unknown Worlds Charlie Cleveland, who told GamesIndustry.biz that the game had sold 5.23m units across PC, Xbox One and PlayStation 4.

That figure doesn't include the 4.5m copies that were shifted during the game's time as a free title on the Epic Games Store.

In other words, around 10m people own Subnautica, which isn't to be sniffed at.

Research firm Newzoo says that the game was played by 0.4 per cent of 'core PC gamers' in November 2018 and 2.9 per cent the following month when it was free on Epic's platform.

The title launched in Steam Early Access back in December 2014 before a 1.0 launch in January 2018. Sequel Below Zero was rolled into Early Access in January 2019, jumping to the No.1 spot in the Steam Top Ten when it was released.