Okay, so PO has an AoO on Cecila's movement, then it's PO's move on 246, no water elemental, but webs entangle him.
Summary (to confirm):
PO is at 100N80E-25Z (15 ft vertical space?)
Cecila is at 105N55E-30Z (10 ft vertical space?)
Webs are 20ft radius sphere centered at 100N80E-10Z, and considered anchored to the walls of the water "trough".
So PO will take a bite as the AoO, but I'll have to get a bit more time and my map to make my next move since I'll need to make sure I get it right with those web.