A method for achieving continuous high precision measurements of atmospheric O2 is presented based on a commercially available fuel-cell instrument, (Sable Systems, Oxzilla FC-II) with a precision of 7 per meg (approximately equivalent to 1.2 ppm) for a 6-min measurement. The Oxzilla was deployed on two voyages in the Western Pacific sector of the Southern Ocean, in February 2003 and in April 2004, making these the second set of continuous O2 measurements ever made from a ship. The results show significant temporal variation in O2, in the order of +/-10 per meg over 6-hourly time intervals, and substantial spatial variation. Data from both voyages show an O2 maximum centred on 50°S, which is most likely to be the result of biologically driven O2 outgassing in the region of subtropical convergence around New Zealand, and a decreasing O2 trend towards Antarctica. O2 from the ship-based measurements is elevated compared with measurements from the Scripps Institution of Oceanography flask-sampling network, and the O2 maximum is also not captured in the network observations. This preliminary study shows that ship-based continuous measurements are a valuable addition to current fixed site sampling programmes for the understanding of ocean-atmosphere O2 exchange processes.