A rebreather apparatus having a gas scrubber canister with a generally
oval or elliptical cross section. The canister being configured so that
exhaled gases pass through the adsorbent in a radial manner through a
generally hollow tube having the same cross sectional shape as the
canister. The shape of the canister allows for increasing the volume of
the canister relative to round cylinder shaped canisters without making
it too cumbersome such that it effects the efficiency of a diver. The
canisters have at least one removable end cap and the end caps are
configured for housing gas addition and control systems. The rebreather
apparatus can be rapidly reconfigured to provide a variety of fully
closed or semi closed circuit configurations and it can be reconfigured
to be worn in a variety of ways based on tasks to be performed and diver
preference.