Methods and systems to provide breathing air to underwater divers in response to the divers' respiration at pressures less than 25 psi above atmospheric pressure during inspiration while delivering no or minimal air during exhalation, by controlling the actions of a pump during the time course of breathing. Methods and systems that sense a diver's need for breathing air, determine inhalation demand or exhalation state, and control the operation of a pump which delivers breathing gas to the diver via a tube. An integrated system for the same which incorporates at least an energy source (26), pump (28), air tube (30), breathing aperture (10), sensor (20), and logic processor (24) is disclosed.
