Blue Hole is a natural freshwater sinkhole located in Mexico, formed by the Santa Rosa sink geological phenomenon. As part of a system of seven sister lakes connected underground, this site features alkaline water with visibility ranging from 6 to 24 metres. The site is accessible via both shore and boat entries and is suitable for beginner divers. Due to the alkaline nature of the water, the environment supports minimal life, though goldfish and crawdads have been recorded here. Divers should note that conditions at this site can vary.