We have carried out an extremely long integration time (9000s/beam) 21-cm blind survey of 60deg^2^ in Centaurus using the Parkes multibeam system. We find that the noise continues to fall as sqrt(t_obs_) throughout, enabling us to reach an H I column-density limit of 4.2x10^18^cm^-2^ for galaxies with a velocity width of 200km/s in the central 32deg^2^ region, making this the deepest survey to date in terms of column density sensitivity. The H I data are complemented by very deep optical observations from digital stacking of multi-exposure UK Schmidt Telescope R-band films, which reach an isophotal level of 26.5Rmag/arcsec^2^ (27.5Bmag/arcsec^2^). 173 H I sources have been found, 96 of which have been uniquely identified with optical counterparts in the overlap area.