Subnautica

Subnautica is an open-world underwater survival adventure from Unknown Worlds Entertainment. Your spaceship crash-lands on an ocean planet, and you end up in a lifepod in the middle of the water with no clear plan but a need to eat, drink and find a way home.

You dive deeper and deeper: gathering resources, crafting tools, building an underwater base and taking the helm of a submarine. The world is made of coral reefs, caves, volcanoes and dark abysses, and the main fear here is depth rather than fighting. Weapons are scarce, so you have to be clever and flee. The story unfolds through signals, wreckage and finds, without a strict guide.

According to HowLongToBeat, the story takes about 30 hours and a full run about 52. In a month at roughly 60 hours you can finish it entirely, with room to spare. The game is single-player and works offline, so the rental limits nothing important. It suits anyone who is not afraid of dark water.