Submerged is a post-apocalyptic exploration game set in a submerged city. It starts by showing how a girl and a little boy approach a submerged city by boat. The boy is sick and is put in a temple to rest. From there on there are three stories to discover. The girl sets out to explore the city by boat, collecting supplies to help the boy, exploring the buildings, finding out if there are inhabitants and whether living in the city affects her. Optionally 60 secrets can be collected that reveal the history of the city and how it became submerged. Finally, after collecting supplies, a part of the boy and the girl's history is revealed. For the latter two the story is told entirely through pictures, stored in a journal.
The girl can explore freely with the boat in any direction and the vessel has unlimited fuel. The game uses a free camera and there is a postcard feature to capture shots from angles that are not available during regular gameplay. There are eight important landmarks to discover, four hotels and eight types of creatures. Interesting points in the environment can be spotted using a telescope when they are nearby and in her line of sight. This leads to the location of supplies, but also the secrets. Optionally 26 boat upgrades can be discovered that provide a speed boost to the boat. Each collected part provides more time to boost.
Once a building has been discovered, the girl has to find a way to access it. She needs to scale the building, using vegetation, pipes, ladders and ledges. Climbing is largely automated by moving in the right direction and it is impossible to fall down or die. Large buildings often have different climbing paths that need to be explored to discover all the secrets. An in-game map can be used to examine areas and find the location of interesting items. The game does not feature combat. After collecting supplies the girl automatically returns to the temple, helps the boy and the story is furthered. The game has a day-and-night cycle, but it does not affect gameplay.