Underwater Cities: New Discoveries has a number of modules which are playable as an expansion to Underwater Cities. This includes the 3 Layered boards, the museum of underwater artifacts and new metropolises.
There is also 52 new cards, some for each deck, and new asymmetric assistants to bring some replayability to your game! You also get additional player boards, as well as upgraded versions of the original ones!
The new expansion requires a copy of the Underwater Cities base game.