Players craft upgrades such as flippers and a seaglide that lets them venture further into the deep.

As they spend more time meandering and gathering resources though, that changes. They know nothing about what can help or kill them in the environment. They move slowly without external equipment. They can stay underwater for a few seconds before coming up for air. Players will build several tools such as this mineral detector in “Subnautica: Below Zero.” (Unknown Worlds) Think of it is as “underwater Minecraft” as others put it, but it’s more narratively focused, up to a point. Because this is a sci-fi survival game in the first person, players have to worry about hunger, thirst, heat and air. It acts as a base as players scout the ocean for resources. That means finding the drop pod from Robin’s crashed ship. “Subnautica: Below Zero” is more about staying alive in the inhospitable underwater environment. It touches on the main story of the original, but players don’t need to know much about the first game to follow it. What she uncovers is a wider conflict that involves an ancient alien race and the deadly Kharaa Bacterium. Robin doesn’t buy the corporate report blaming her sibling’s demise on “employee negligence,” so she’s on the planet to see for herself.

Her initial mission is to investigate the mysterious death of her sister, Samantha, who was working on this alien world for the interstellar company Alterra. It’s a title that fits squarely in the survival genre as Robin has to stay alive after she crash lands on Planet 4546B. This is the world players encounter in “Subnautica: Below Zero,” the sequel to the 2018 hit.

Even when she’s indoors, she sees the danger of ocean breaching the hull and drowning her. If it’s not the wintry weather on the surface threatening her with hypothermia, it’s the creatures of the ocean world trying to eat her while she’s exploring the deep. Scientist Robin Ayou is alone on a strange planet and everything is trying to kill her.

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