I keep mine connected via a coiled lanyard. The Clip kind like Larry said. on descents, at times, I let it hang if I am busy trying to clear my ears while dumping air...once I'm down, I unclip it so I can use it at arm's length (Its a PnS....with a strobe and heavy base/handle).
I have been in very heavy current whereby I had to use both hands to hang in place on rocks and pull myself into sheltered spots....been flapping like a flag on a pole in serious currents during safety stops hanging onto a rope with both hands.....Some of these times, I have had to have both hands free to help. A camera on my wrist would/could have gotten in the way. As much as I would have rather held the camera close to me and lower my profile, I absolutely had to use both hands (unhindered)...In one case, it was to hang on to a panicked diver to prevent her from being dragged out into the blue and into downcurrents....(Very unpredictable at times at Sipadan's Barracuda Point for example). During these times, my camera was dangling and the arms (Ultralight Ball joint) pushed/folded flat from the current. Never though was I worried about losing my baby and I was free to concentrate on dive conditions/issues at hand.
I am sure that if I had it on my wrist, it would have certainly smashed to bits against the rocks as I was hanging on clawing my way to safety...Having said that, I never let go of my camera and let it dangle unless I really need to. Its held close against my chest ready for that next shot....I am sure its the same for everyone...