Thanks!
DA Aquamaster once bubbled...
A reef hook is a small metal hook attached to a short line that you hook into the subtrate or rocks underlying the reef. (you don't want to plant it in the middle of a living coral head.) I am not aware of anyone who sells them and they are a little controversial, particularly with the extreme folks who think divers should not wear gloves to ensure they don't touch the reef.
Personally, I think using a reef hook is a far better option for a diver than holding onto the reef in a current and I think they offer saftey advantages if a down current is encountered. A reef hook also has applications in freshwater where a diver may be diving in a river with a rocky bottom and strong current.
A reef hook may not be all you need however. In my expereince I have noted that many regs with soft rubber or large sized purge buttons or large forward facing holes in the front cover will free flow when hooked on and looking up current. It's one of the reasons I switched to a D400 second stage several years ago.
This link covers the controversy as well as how to make one.
http://www.divernet.com/technique/0101hook.htm