They are. you can see an example of them in the water - breathing script in the entitybank\waterScripts folder.
setup a square room and add a trigger zone. in the main AI assign the water script. This can be anywhere on the map.
Place another trigger zone and assign this ones main ai to water - breathing. Set a marker and a light or two and build the test game.
If the water is to high or to low, then you can press the page up or page down key to adjust it. Get the water about half way deep in the level.
Walk to the trigger zone with the breathing script and Crouch in the water. Notice the breath hud in the top left and how it decreases when you are underwater and increases when your head is above water.
Open the water - breathing script to take a look how it was done.
This script works great. Do keep in mind if you use edit pad it will squack a bit because the new 118 commands are not in the database. Turn auto syntex checking off for this script.
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