Even with bright red water, the pond center shows 0.42,0.37,0.30 — NOT red. The water disc is NOT being rendered at the pond center. But pond_west (5,-5) shows a lighter color (0.62,0.56,0.48) — slightly different, maybe the dock. The water disc is missing/covered.

Let me check if the pond water disc is actually inside the ground mesh. The ground mesh has 130x130 segments over size 34 — the grid spans -34..34. At the pond center the ground dips to -1.19. But wait — maybe the ground at the pond edges RISE above 0.25 and the water disc is fully buried? No — the center dips to -1.19, well below.

Hmm, let me check the water disc radius vs the pond depression. The depression function: dp < 6.4 → h -= 1.5*(1-t²)². At dp=6.4, h -= 0. At dp=4, (1-0.39)²=0.37 → h -= 0.56. At dp=0, h -= 1.5. The water disc radius is 7, which covers dp up to 7 > 6.4. So the water disc is bigger than the depression — its outer rim is buried in the ground (ground at dp 6.4-7 is above 0.25? terrain at dp=6.4: base 0.35ish minus 0 = 0.35ish → above 0.25, so the water disc rim from dp 6.4 to 7 is underground). That's fine — the visible water is the central part.

But the render shows NO water at the center. Let me check if the pond water object's mesh normals are flipped (inverted) — if normals point down, the camera sees the backface (culled in Cycles for transmission? no, Cycles renders double-sided by default... actually with transmission, backfaces matter).

Let me check the water disc normal direction.

import bpy
pond = bpy.data.objects['PondWater']
# check face normals
import numpy as np
for f in pond.data.polygons[:5]:
    print('face normal', f.normal, 'z sign', f.normal.z)
print('face count', len(pond.data.polygons))
# check if the mesh has the circle cap on top
for v in pond.data.vertices[:5]:
    print('vert', v.co)
# check bounds
print('bounds', pond.bound_box)