This is an expansion and requires the base game to play: Yes

Explore a new underwater society in Pearlbrook, the first expansion for Everdell!

Pearlbrook introduces a new side board, the river board, where you'll send your frog ambassador to gather a new resource: pearls. You'll also encounter new aquatic critters and constructions! Collect enough pearls and you can construct fabulous wonders and adornments, to make your city the pride of Everdell!