Not all "emergencies" need to end a dive. I jumped in one time had forgotten to buckle my BC to the tank :doh2:. Once we hit bottom I was able to sign "tank strap loose" and my buddy buckled me up and we were on our way. I would have hated to have had to remove all my gear underwater to do it on my own if I had to.
So signal "problem" and motion to tank strap. Any buddy with an IQ above room temperature should be able to look behind and see and fix the problem. Or just dekit and do it. Its not difficult and again doesn't require learning an entirely new language which well maybe completely useless in the real world, especially outside the usa.
Im still struggling to see the NEED for a comprehensive sign language in diving when you can do 99% of diving with standard signals and the other 1% with proper UW comms.