Seadeuce:May not help, at least in Cozumel[/
It did for me, albeit not in Coz., but clawing was not an option at that site.
One need to be correctly weighted though, to have the benefit of all the lift available from the jacket.
Not something that you would easily forget ..
Seadeuce
There was an incident several years ago (it may have been reported here) with a half a dozen experienced divers took chamber rides in Coz because of down drafts. They all inflated their BCs.
I experienced one that dragged me down a sandy hillock on San Francisco Reef to about 140 feet until I let go and started kicking like a banshee towards open water. Scared the bejezzus out of me.