DAN does not recommend that symptomatic divers be recompressed while breathing standard air in the water. In some areas of the world, divers are treated with in-water recompression because of a lack of chamber facilities.
At one time, divers were treated in recompression chambers using the U.S. Navy treatment tables and breathing air instead of oxygen. The failure rate was high. It is unlikely that in-water recompression using air is more effective than those old treatment tables. In-water recompression with the diver breathing oxygen instead of standard air has been used successfully in some areas.
However, in-water recompression has its own dangers and should not be attempted without the necessary training and equipment, or in the absence of someone who can assess the diver medically. The resources required for in-water recompression usually exceed the ability of those at the scene to properly assist the injured diver.
In-water recompression of any type is not currently recommended by DAN.