Blue Hole (New Jersey)
The Blue Hole is located in the Pinelands of Monroe Township, Gloucester County, New Jersey and Winslow Township, Camden County, New Jersey. It is a clear blue body of water situated in the middle of a dense forest, with many similar such lakes in its immediate vicinity. The water has warm and cold spots, averaging 58 to 60 degrees Fahrenheit. The color is very unusual, as most lakes and ponds in the area are brownish due to large deposits of bog iron and the presence of tannic acid. The Blue Hole is circular and about across. In the 1930s, the Blue Hole was a popular party and swimming spot. A wooden footbridge over the Great Egg Harbor River that once made the Hole easily accessible was wiped out by a storm in the 1960s; now it can only be reached on foot.
Devils Hole
Devils Hole is a geothermal pool within a limestone cavern in the Amargosa Desert in the Amargosa Valley of Nevada, east over the Amargosa Range and Funeral Mountains from Death Valley. Its waters are a near constant salinity and temperature (). The cavern is over deep and the bottom has never been mapped.
Devils Hole branches into deep caverns at least deep from an opening at the surface that is approximately . According to geologists, the caves were formed over 500,000 years ago. The pool has frequently experienced activity due to far away earthquakes in Japan, Indonesia and Chile, which have been likened to extremely small scale tsunamis.