Scuba diving is a mode of underwater diving in which the scuba diver uses a self-contained underwater breathing apparatus (scuba) which is completely independent of surface supply, to breathe underwater. Scuba provides the diver with the advantages of mobility and horizontal range far beyond the reach of an umbilical hose attached to surface-supplied diving equipment (SSDE). Scuba divers engaged in armed forces covert operations may be referred to as frogmen, combat divers or attack swimmers