By far the most traditional of the non-chamber treatments of DCS is underwater recompression therapy. In this situation the water, instead of an RCC, exerts the pressure. Air supply is usually from compressors sited on the diving boat. Although this treatment is frequently disparaged, it has often been the only therapy available to severely injured divers, and it has had many successes, most of which have never been reported. This was certainly so in those remote localities such as Northern Australia, in the pearl fishing areas, where long periods were spent under water and standard diving equipment was used.
The failure of DCS to respond to recompression therapy is often related directly to the delay in treatment. Sometimes chambers are not readily available. For this reason, underwater air recompression was effectively used in Hawaii, with good results, within minutes of symptoms developing. This was also the experience of professional shell divers of Australia, at least until underwater oxygen therapy became available.
Despite the value of underwater air recompression therapy, many problems may be encountered, and this treatment should not be entered into without appropriate planning and resources.
Most amateurs or semi-professionals do not carry the compressed air supplies or compressor facilities necessary for the extra decompression. Most have only scuba cylinders or simple portable compressors that will not reliably supply divers (the patient and the attendant) for the depths and durations required. Environmental conditions are not usually conducive to underwater treatment. Often the depths required can be achieved only by returning to the open ocean. The advent of night, inclement weather, rising seas, tiredness and exhaustion and boat safety requirements make the return to the open ocean a very serious decision. Because of the considerable depth required, hypothermia becomes likely. Seasickness in the injured diver, the diving attendants and the boat tenders is a significant problem. Nitrogen narcosis produces added difficulties in the diver and the attendant.
The treatment often has to be aborted because of these difficult circumstances, thereby producing DCS in the attendants and aggravating it in the diver. Although in the absence of an RCC it may be the only treatment available to prevent death or severe disability, it should never be undertaken without careful consideration of the resources available and the environmental conditions.