Don’t Starve’s new expansion will be washing up on the Steam Early Access program December 1st. Its name is Shipwrecked, and it will be a single-player expansion only, as far as we can tell. It’s going to feature new playable characters, biomes, creatures, and seasonal effects. According to the Don’t Starve wiki page, the biomes will include beach, jungle, marsh, ocean (shallow), and ocean (deep).
The season’s list only includes Hurricane season, but since its “seasons” plural, we could assume there will be more added in the future. A few notable creatures are water creatures like the Tiger Shark and Bottlenosed Ballphin, which obviously means there will be some sailing and ocean combat.
The developers want players who enter Early Access to know that like all Early Access content, there will be frequent updates, bugs, and tweaking of those bugs. If there is a bug, they want players to report them on their forums.