In Subnautica: Below Zero, the sequel to Unknown World's superlative Subnautica, you're once again back on planet 4546B, crash-landing rather spectacularly on the frozen far side of the alien world this time around where you're immediately thrown into a mystery surrounding the fate of your missing sister, Sam. It may have a slightly smaller map (this was originally planned as a generous dollop of DLC after all) and a little less variety in terms of its biomes, but this follow-up still feels like an essential experience, one that delivers more of the series' signature survival excellence whilst also smoothing over some of the rough edges of its predecessor's core gameplay loops.

Everything feels that little bit easier to manage in Below Zero. You'll get off the starting blocks more quickly here, breezing through the early game's lack of oxygen and mobility options and pretty much straight into spinning around on your Seaglide in a much more straightforward and smooth manner, before getting your hands on a bunch of brand new vehicles that, by and large, improve upon those found in the original Subnautica.

The story this time around is also a much more fleshed out affair with cutscenes, a fully-voiced protagonist and other characters with whom to converse, and although we definitely preferred the total isolation of the original's narrative, what's here still manages to remain engaging for its duration, throwing up some cool surprises along the way without making the critical mistake of impeding upon your time spent crafting, exploring and building.

In fact, if Below Zero does make one major error for us, it's in its decision to expand upon the very brief on-foot sections found in its predecessor. There's far more marching around here, wandering the hostile arctic tundra, and although it's never particularly bad - there's always plenty to find (and flee from) in these portions of the game - it's just not where Subnautica really excels, we always wanted to be back in the water as soon as we were dragged out of it. There's also not quite the same scale and scope in the tech tree here, which is understandable given this sequel's DLC origins.

However, slight niggles aside, Below Zero absolutely delivers in providing more of the excellent deep sea survival antics that we know and love from the original Subnautica. This is a super solid port too, a joy to sink time into in both docked and portable modes, with only a little stuttering here and there as you enter new biomes - and the series' ever-present scenery pop-in - to mention in terms of technical shortcomings. Unknown Worlds has served up another superb slice of survival shenanigans here, one that we highly recommend diving right into.