In Seasick, you try to push back against the impending demise and adapt to the new harsh conditions in the ocean, with a twist: there's no enemy to take the fight to directly. Instead, you manage the trash coming your way by moving it, or your units, out of the way, collect evolution points to increase your odds of survival and try to endure deadly events such as oil spills or erupting volcanoes.
The Demo version of Seasick contains the following features, with more coming in the full release:
The environment (game "board") consists of three depth levels
9 Different types of trash to defend your units from
8 Different kinds of adaptations that help your units survive
4 objectives to strive towards to finish the game