This dataset contains measurements and estimates of sea water properties from a PhD project in North Sulawesi. The data were collected from December 2006 to July 2007 in the coral reefs around the islands Bunaken and Gangga and near the city Manado. Secchi depth was estimated by lowering a Secchi disc from a boat. Salinity was measured with a Refractometer. Tidal cycle information was taken from a tide calendar. Wind speed was estimated based on wave development. Underwater visibility was estimated by divers and water temperature was measured with a dive computer (Suunto Favor).