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For me, the main advantage of a Jon line is to isolate the jerking of the anchor line in sloppy seas -- a common issue on wreaks like the Doria. A typical anchor line in heavy seas has a 3 to 5:1 scope so is more horizontal than vertical. Hanging onto the line directly can yank your arm out of its socket everytime the bow lurches in the swell.
I also find using 1"/25mm soft webbing is more tangle resistant than line. Same with Reef Hooks.
For me, the main advantage of a Jon line is to isolate the jerking of the anchor line in sloppy seas -- a common issue on wreaks like the Doria. A typical anchor line in heavy seas has a 3 to 5:1 scope so is more horizontal than vertical. Hanging onto the line directly can yank your arm out of its socket everytime the bow lurches in the swell.
I also find using 1"/25mm soft webbing is more tangle resistant than line. Same with Reef Hooks.
unless im diving in strong current on a regular basis i wouldn't use one - just another piece of gear to fiddle with
I carry one for NE wreck diving. I use it for two reasons. One is to get some distance from the line when it's jerking up and down. The other is to get some distance from the line when 8 people are already trying to hold a 20' stop on it. If neither is a problem, I just hold the line. I probably hold the line about half the time and use the jon line the other half.
Great points, curious what length of hangs you have? Anything longer then 15 minutes you should really consider using it all the time just to reduce risk of possibly hit in wrist or elbow from the strain.