Before the first full-detail water read lands (it can take many seconds
from cold tiles), a refresh's loaded-tile read with one low probe still
dropped a river height to the geoid. Before that landing, loaded-tile reads
may now find raised water but only a full-detail read lowers it.
CURRENT-STATE also says what the earlier fixes changed: C stays the CCTV
shortcut when the bridge cannot be entered, voice entry is refused on a
bridge, and the ridden ship's trail is hidden with its sprite.