Function water_radius 

pub fn water_radius(radius: f32, water_height: f32, height_scale: f32) -> f32

World radius of the analytic sea-level sphere: the terrain surface radius evaluated at water_height. water_height = 0.5 is the baseline — the noise midpoint / custom h = 0 line — at which the sea sits exactly at radius. At the shipped defaults (CesBuilder::water_height 0.549, CesGPUNoiseExample’s height_scale 0.0585) it sits slightly above, at 1.0069 * radius, so terrain pokes through to form seas/lakes wherever the height rises above water. Lowering the level drains the seas; raising it floods low land.