Crossing the surface was a step change. The underwater tint did not start
until the eye was 1.5 units down, and when it did it covered the whole
screen at once — so there was a dead zone at the surface, then a pop, and
never a waterline. What the camera showed in between was the water plane
seen edge-on: a razor-straight horizontal cut.
The overlay now takes a boundary rather than covering everything. It runs
from off the bottom of the screen to off the top as the eye moves through
a band around the surface, so the waterline rises past the lens instead of
switching, and the edge carries a small ripple so it does not read as a
straight cut. Fully submerged puts the line past the top, which is the
previous behaviour exactly.
The tint also builds from the surface now rather than from 1.5 down, with
a floor held through the crossing so the submerged half reads as water
rather than clear air.
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