A recent review of crown-of-thorns starfish (Acanthaster planci; COTS) in Indonesia has suggested that their impacts have gone under-reported. In 2012-2013, we surveyed COTS at permanent transects within 12 sites of the Spermonde Archipelago, Indonesia, a coastal region close to two rivers and the heavily urbanised city of Makassar. Evidence of COTS was apparent at 8 of 12 sites surveyed with highest densities (37 starfish per 250 m(-2) at Barrang Lompo) comparable to those reported in the Indonesian historical literature. At Barrang Lompo and Bonetambung, the COTS outbreak resulted in the loss of half the live coral. Terrestrial effluents have reduced water quality in the Spermonde Archipelago, which further supports recent work linking water quality and COTS outbreaks, thus providing a warning of future outbreaks to Indonesian coastal managers given the country's increased urbanisation.