We present results from a spectroscopic study of ~4000 galaxies in a 6.2 square degree field in the direction of the Aquarius supercluster and a smaller typical field region in Cetus, down to R<19.5. Galaxy redshifts were measured using the Two Degree Field system on the Anglo-Australian Telescope, and form part of our wider efforts to conduct a spectro-photometric and weak gravitational lensing study of these regions. At the magnitude limit of the survey, we are capable of probing L_* galaxies out to z~0.4. We construct median spectra as a function of various survey parameters as a diagnostic of the quality of the sample. We use the redshift data to identify galaxy clusters and groups within the survey volume. In the Aquarius region, we find a total of 48 clusters and groups, of which 26 are previously unknown systems, and in Cetus we find 14 clusters and groups, of which 12 are new. We estimate centroid redshifts and velocity dispersions for all these systems. In the Aquarius region, we see a superposition of two strong superclusters at z=0.08 and z=0.11, which both have estimated masses and overdensities similar to the Corona Borealis supercluster. Comment: Replaced with version accepted for publication in ApJ. Text reduced. Science unchanged