Thalatossa is an immersive serious game that aims to showcase marine environments and the various threats looming over these ecosystems through exploration, resource management and combat. It takes the form of a first-person Action-Adventure game set in an oceanic world featuring a wide array of natural and artificial marine habitats across five regions—temperate, tropical, polar, open ocean, and abyssal—which can be explored by boat or through diving. Throughout the journey, the player will have to manage resources and survive encounters with enemies that serve as symbolic representations of threats to marine biodiversity. Each enemy takes the form of a humanoid sea creature with an appearance reflecting the specific issue it embodies, while its behavior and abilities are directly inspired by the harmful effects of those threats, and must be vanquished to proceed.