This is a copy of a post in Ontariodiving.com by Marc Belair. He gave me permission to post it here to get some ideas from members here who have extensive experience in diving in overhead environments.
Though some members of our forum have formally/informally discussed this topic, it came back to the surface yesterday when a diver was recovered 400' from the hole in quarry yesterday. Though no details of the accident have been released (gear, training), what is known was that the diver was diving alone and did not have a continuous guideline to the surface.
When our group ice dives we all use our skills from our cave training to conduct the dive as safely as possible. The one main difference (on OC) is that we always dive with a stage and breath off of it. If there happens to be an issue with a free flow, the dive is called, and you feather your stage valve until the exit. Back gas is used as reserve only.
To get an idea of how the dive is conducted, I've included a link to a video i made a few weeks back. http://www.vimeo.com/3160312
"Under Ice Diving?
For over a decade, ideologies have been in opposition as to how to dive safely under the ice.
The first technique with a tethered diver with tender and safety diver at the surface proved reliable and all agree to say that it is safe. It allows almost any diver with a bit of experience and a short training to go under the ice and see what the frozen environment looks like, widening his horizons a little. The major disadvantage of this technique lies in the limits which it imposes and in its repetitive aspect. For one who dives one or twice per year under the ice and begins in the sport, it can be fully satisfactory. It can also meet the needs for seasoned divers who simply feel the need to make bubbles during the winter interval.
The second method makes use of techniques developed in caves and which have proven to be reliable there. Divers who have the proper training, equipment, experience and the rigor can venture much further while maintaining a continuous link to the surface. The caving techniques can be applied as such to our winter environment but require being adapted according to the goals of the dive and the particular conditions of the medium. It should be questioned if the technique can be adapted to certain environments. To dive the St-Lawrence River with its current, its quasi infinite space and the temperature of its water barely above the freezing point is perhaps not such a medium. I personally decided that the risks where just too high several years ago.
The major problem with the second technique lies in the level of improvisation with which one sees this technique applied. Many divers with little or not experience, inadequate equipment, an obvious lack of preparation and formation venture where they should not go.
Scuba diving is a sport which attracts by its nature, people who seek adventure. Not all divers are willing or can afford to go to Florida or Mexico to follow a formation which will be applied here under ice a few times a year. Not all divers are willing or can afford suitable equipment.
People will take short cuts and will cut try to save moneys on their training and equipment while thinking that they will manage. In the majority of the cases, the diver returns unscathed to tell his tales, some unfortunately will end their life in an ice covered hole.
We need to lay down rules of formation for this practice. Based on the rules of diving cave and modified according to the medium. Tom Mount of IANTD is ready to endorse such a training program but waits until an instructor with the necessary experience builds the program. The training offered for cave diving made it possible to considerably reduce the number of deaths in caves; an equivalent training for our ice caves could possibly have the same effect.
Marc Belair"
Scott
