Aktun Koh - "Puma Cave" in Mayan
This system had the same halocline issues as Chac Mol. Following two massive hurricanes in the fall of 2006, the fresh/salt water mixing zone thickened to several feet and shifted the depths, so that most of the line in the first several hundred feet of the cave was in that mixing zone. This made the photography a challenge since you had to ensure that there was no mixing around the lens, the model or anywhere in between.
Aktun Koh upstream and more so downstream lines had Swiss cheese zones mixed in with greatly decorated rooms, but trying to shoot in and around the halocline was next to impossible, so my shots definitely do not do justice to that cave. Upstream main line started shallow, went up and down with reach jumps all over the place starting within one to two feet of main line and sometimes going parallel to that line for a while. The line went in a huge circle and eventually came back to the beginning ending about a foot short of actually joining back into itself. The recent hurricane resulted in a part of the cave collapsing a section of that loop.
Downstream section is definitely more beautiful and supposedly gets even prettier once you reach the T and go left. As a result of halocline being all over the place and the fact that we had to stay right on the line due to amount of reach jumps all over the place, we could not find the spot where halocline would not be present, so the pictures really do not show the beauty of that cave.