STILL the same colors! Moving the water disc to (8,-7,0) didn't change the render at all — the exact same pixel values. That means the pond water object is NOT being rendered at all, regardless of position. The pond center (0.67,0.2) still shows dirt.

The pond water disc might be hidden behind the GROUND MESH. Wait — the ground is a huge mesh, and the pond depression is cut into it. But the ground at the pond center is at -1.19, water at 0.25... unless the ground mesh has some faces ABOVE the water.

OR — the pond water disc is inside the ground and the ground is opaque, so from the camera angle, the ground's far side (the pond's far rim, which is ABOVE 0.25) occludes the water. The pond far edge is at (8,-13.4) with terrain 0.33 — above water. The near edge (8,-0.6) terrain 0.42 — also above water. So from the camera at (15.5,-15.5,5) — the camera is SOUTH of the pond. The pond's far side from the camera is the NORTH rim (y=-0.6, at 0.42 height) which is between the camera and... no wait, the camera is south, so the north rim is on the far side. The near rim (south, y=-13.4) is at 0.33 — higher than water 0.25. From a camera at height 5 looking down, the near rim (0.33) would block the view of the water immediately behind it.

But the pond center at (8,-7) is 6.4 units away from the near rim — the water surface should be visible beyond the rim. Unless the rim is tall enough to occlude. The rim at 0.33 vs water at 0.25 — only 8cm higher. From a camera 20 units away at height 5, an 8cm rise at 6.4 units would block the water surface behind it for a distance: the line of sight from camera (height 5) to the water at distance d... the geometry: camera at (15.5,-15.5,5), looking at water at (8,-7,0.25). The ray passes over the near rim (8,-13.4,0.33). The rim is only 0.08 above the water. From the camera's perspective, the ray to the pond center passes at height...

Camera to pond center: direction (-7.5, 8.5, -4.75). Parametrize: P(t) = camera + t*dir. The near rim point (8,-13.4): from camera, delta = (-7.5, 2.1, -4.67). The ray to pond center at the y of the rim... this is getting complicated. The point is, the rim might be occluding the water because the terrain rises above the water level all around.

Actually — the fundamental problem: the pond depression is only 1.5 deep, and the water fills it to 0.25. The terrain around the pond (at radius 6.4+) is at ~0.35-0.55, only slightly above the water. From a low camera angle, the water surface is barely visible. The water should still be visible at the center though.

Let me test more directly: render from straight above the pond to see if the water disc is there at all.

import bpy, os, tempfile
import numpy as np

# Temporarily point camera straight down at pond
cam = bpy.data.objects['Camera']
old_loc = cam.location.copy()
old_rot = cam.rotation_euler.copy()
cam.location = (8, -7, 20)
cam.rotation_euler = (0, 0, 0)

out = os.path.join(tempfile.gettempdir(), 'check_top.png')
bpy.context.scene.render.filepath = out
bpy.ops.render.render(write_still=True)
print('rendered', out)

img = bpy.data.images.load(out)
w, h = img.size
px = np.array(img.pixels[:], dtype=float).reshape((h, w, 4))[..., :3]
print('center rgb', px[h//2, w//2].round(3))
print('mean', px[..., :3].mean(axis=(0,1)).round(3))
# sample around center
for dy, dx in [(0,0),(100,0),(0,100),(-100,0),(0,-100),(200,0),(0,200)]:
    print((dx,dy), px[h//2+dy, w//2+dx].round(3))
bpy.data.images.remove(img)

# restore
cam.location = old_loc
cam.rotation_euler = old_rot