Diffuser (breathing set part)
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A diffuser is a device fitted over an underwater breathing set's blowoff hole to break up the resulting bubbles very small so they will not be seen from out of the water. They are mostly needed in frogman-type diving operations where secrecy is needed, and in marine biology to avoid scaring fish which are being studied. Designing an adequate diffuser on a rebreather is much easier than on open-circuit scuba.
