The pond center STILL shows dirt color (0.42, 0.37, 0.30). The water isn't rendering. Let me investigate — maybe the water disc is being covered by the ground mesh. The ground is a 130x130 grid at size 34, and at the pond the terrain dips to -1.19, but the ground mesh at that point is still a continuous surface — the water disc at z=0.25 sits ABOVE the ground there... unless the ground has vertices that rise above.

Wait — I need to check if the water disc actually covers the camera-ray intersection. The camera ray to (8,-7) at z=0.25 — the ray hits whatever is first. The ground at (8,-7) is at z=-1.19, so the ray should hit the water disc at z=0.25 first. Unless the ground is rendered as a big flat plane at some higher z... Let me check the actual vertex heights of the ground mesh near the pond.

import bpy, math
import numpy as np

ground = bpy.data.objects['Ground']
# find vertices near pond center
verts = np.array([v.co for v in ground.data.vertices])
# ground mesh is in object space (object at origin, no transform)
near = verts[(np.abs(verts[:,0]-8)<2) & (np.abs(verts[:,1]+7)<2)]
print('verts near pond center:', len(near))
print('z range', near[:,2].min().round(3), near[:,2].max().round(3))
print('sample z', near[:5, 2].round(3))
# pond water disc vertices
pond = bpy.data.objects['PondWater']
pv = np.array([v.co for v in pond.data.vertices])
print('pond verts z range', pv[:,2].min().round(3), pv[:,2].max().round(3))
print('pond verts count', len(pv))


verts near pond center: 64
z range -1.229 -0.633
sample z [-0.795 -0.988 -1.104 -1.096 -1.004]
pond verts z range 0.25 0.25
pond verts count 72