Go to the big map room w/e it's called, and scan yourself while proning, and then while standing, and then again proning * keep searching for changed value*
But for an easier way, If im correct, Swimming is the same adress, just another value..
Prone
stand
crouch
climb
swim
???
Those are all on one adress, so take the swim adress, and then go prone in a big map, and there is it's value ;D