As per said in the below screenshot, one may break through without tanya swimming in that chunk of water, resulting nothing triggered. This bug won't alter later game play except one have to scout the area by oneself unless one let tanya get into the water, which looks awkward. (probably to test the water temperature lol)
The bug is quite easy to fix, either move the trigger a bit south-eastwards, or replace that line of sand bags with concrete walls.
This screenshot is taken under Normal difficulty, but the bug itself is still valid in Mental version. (I didn't beat the later part of the level though)
Edited by jackomatt, 09 February 2017 - 02:22 PM.