The number of colony-forming units (CFU) of bacteria belonging to the genus Enterococcus. This indicator bacteria has been correlated with the presence of human pathogens (disease-causing organisms) and therefore with human illnesses such as gastroenteritis, diarrhea, and various infections in epidemiological studies. As such, it is commonly measured in beach water quality monitoring programs.

The State of Hawaiʻi monitors its marine coastal waters using the U.S. Environmental Protection Agency (EPA) 1986 Ambient Water Quality Criteria for Bacteria. A water quality alert is posted if either: (a.) the latest water sample exceeds 104 CFU/100 mL of Enterococcus, or (b.) the geometric mean of the past 30 days of water samples exceeds 35 CFU/100 mL.