Let's add the delta swamp biome.

Delta swamps form where rivers meet the sea. This biome—inspired by the Danube Delta—can appear in various sizes. At night, a "ghost fisherman" spawns; if you place him in a boat, he generates light with his turquoise aura as the boat moves forward. Three new fish inhabit the biome: catfish, carp, and grass carp. Catfish and carp can be used to make fish soup. The biome’s signature tree is the water-leaning willow. I think exploring the marsh at night is a great experience!