terrain.noise_base_lakeIsland shape

The lake noise works alongside noise_base_land on the map's land layout. At its default it mostly ADDS a little land, and its low dips are what pinch off into interior lakes. The real lake knob is offset: raise it toward 0 and big lake systems open up across the island; lower it and the lakes vanish.

Raise offset to 0 and the interior fills with proper lake systems while the island actually grows a little; drop amp to 0 and lakes disappear and the coastline pulls IN (more ocean).