The prevalence of Cryptosporidium spp. in sea (48 samples) and drinking water (10 samples) from the Sinop province, Black Sea, Turkey were investigated by acid-fast staining method. Ten litre samples of water were collected over 12 months from December to November 2011 for Cryptosporidium oocysts detection by acid-fast staining method. Cryptosporidium oocyst were detected in 46 out of the 58 samples (79.31%; 2-46 oocysts per 1 litre) in the water samples from Sinop by acid- fast stain. When a portion of the sea water samples taken from different sources in Sinop city center were positive by acid-fast stain there was no any contamination in drinking water samples. This study point out the need for regular and better monitoring of water-borne protozoans in sea water in Sinop city. In addition, then we need to focus on the important point that are monitoring of water supplies by molecular analysis in order to specify whether the parasites asset in this samples are human pathogenic or not