In celebration of World Oceans Day, Subnautica is on sale now through Monday, June 11 at 6pm BST / 10am PST. 

The deep sea survival game's weekend Steam sale lops 20 percent off its regular price—now £15.59/$19.99—with 15 percent of net developer profits going to sea life charity Whale and Dolphin Conservation. 

In her glowing 89-scored review, Pip suggests a "smattering of technical issues keep Subnautica from true legendary status, but only just". At that point, she'd clocked over 120 hours in the drink, and had snapped over 2,000 screenshots of its beautiful world and strange creatures. I like this excerpt:   

You'll likely discover the stunning kelp forests early on, basking in their green splendour for a moment before spotting the accompanying eel/crocodile creatures. They're Stalkers. They might try to take a bite out of you but they prefer to play with the metal of wrecked craft.

As you poke around you start to find (or be fed via radio broadcasts) suggestive snippets which hint at a story beyond your own survival exploits. How you choose to balance pursuit of the written narrative against whatever you fancy doing under the sea is left up to you, though. Several game modes allow you to make that choice more explicit. For instance, Creative mode strips out all the survival and the story, just letting you build and explore. Hardcore gives you only one life and no oxygen warnings so is better for role-play.

Speaking to the charity's collaboration with developer Unknown Worlds Entertainment, the WDC's Abbie Cheesman says: "Subnautica has been incredibly popular with our supporters in the gaming community and the broadcasters and fundraisers who have taken part in our Gamers for Orcas fundraisers, so we are delighted to be working with the team behind Subnautica on a special promotion this World Oceans Day."

Subnautica is the game that gave Andy the experience he wanted from No Man’s Sky, and, besides Pip's review, I understand it's one of the the best underwater games on PC. I'm yet to play it, but I think I'll dive in this weekend. It's Steam page is this way, if you fancy doing so too.