Don't go ballistic with your blob
THE practice of deploying a delayed Surface Marker Buoy (SMB) towards the end of a dive has done much for diving safety. However, as many divers have discovered, there are potential problems associated with this technique.
I regularly read reports of divers being dragged into an uncontrolled buoyant ascent as a result of using a delayed SMB. Such ascents carry the risk of lung damage and missed decompression, and can be lethal.
The classic scenario goes like this: the diver starts to fill the delayed SMB, the SMB is released, the reel jams, and the diver is pulled upwards, unable to release the reel. He or she cannot dump air fast enough to control the expanding buoyancy of his or her suit and/or BC, so hits the surface after an extremely rapid ascent. In some cases the buddy is also dragged along for the ride.
A few pieces of advice are worth bearing in mind:
Never have a delayed SMB fastened to you when you deploy it, and if it jams, let it go. However, be warned: even this action does not provide complete immunity to diving's equivalent of a white knuckle ride. A diver's glove, finger, or hand may be trapped in the line, reel, or lanyard, so you may not be fastened to it, but it becomes fastened to you!
If possible, launch the delayed SMB while you are still on the seabed to avoid the problem of maintaining depth mid-water while fumbling with the buoy.
Whenever you can, fasten the reel to something on the bottom when deploying it. Again, this is not an infallible approach as one pair of divers recently proved. They tied the reel off, deployed the buoy, and when they untied the reel they discovered that the buoy had not reached the surface.
Finally, train properly for delayed SMB use, and always check your reel before a dive.