I can't for sure but all of our rescue training says no to bowline's. I know that if they don't have pressure on the all the time they can loosen on their own. Doing the half hitches locks the bowline which helps. Working on a mast is constent pressure.bradshsi:Can you explain why you wouldn't use a bowline ?
I can't (and am not qualified to), comment on ice diving, so please don't take my comment as advice. I'm only curious about why a bowline would be a no-no for life support applications.
For working at height (at the top of 60 ft sailboat masts), we would commonly use a bowline. For extra security I tie two locking half hitches after the bowline.
The only time I have ever seen a bowline fail is when the knot was not snugged tight, there was an insufficient tail left in the rope and it was in a load cycling environment (i.e. tied to the corner of a very big carbon/kevlar sail in 40 kts of breeze).
As far as ice goes we have been trained to use a figure eight with a locking beaner. With the beaner who cares how easy it is to untie. It can be untied when it's thawed out.
We also hear of people using their BC as a harness instead of a seperate harness. That is also a no-no. Or they will put a harness over a BC, another no-no.
I for one do not was a knot that is easy to untie when my bacon is on the line.
Gary D.