- underwater_fog.gdshader: rewritten shader_type fog with depth-based color/density + current wave
- water_surface.gdshader: new spatial shader for water ceiling at y=60 with Fresnel + vertex waves
- caustics.gdshader: rewritten with caustic_pattern() function, additive blend, depth fade
- godrays.gdshader: rewritten spatial (was canvas_item) with vertical + depth fade, loop-based rays
- UnderwaterEnvironment.gd: spawns FogVolume with custom fog shader, volumetric_fog_density=0.05
- GodraysOverlay.gd: MeshInstance3D quad child of camera, updates fade_bottom from camera depth
- CausticsLayer.gd: 3 horizontal caustic planes at -5/-15/-25, follow camera XZ
- WaterSurface.tscn: PlaneMesh 2000x2000 at y=60 with water_surface shader
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
