Blue Hole (Castalia)
The Blue Hole captured the public’s interest because of its size, about in diameter, clarity, vibrant blue hue, and enigmatic "bottomless" appearance. Contrary to prevalent belief, the depth of the Blue Hole is not unknown, but has been sounded and found to be about deep. Water temperature is about throughout the year. Floods and droughts have no effect on temperature or water level. The Blue Hole is fed by a passing underground stream which discharges of water daily into Sandusky Bay to the north, feeding into Lake Erie. The water contains lime, soda, magnesia and iron, and because the Blue Hole is anoxic, it cannot naturally sustain fish. The surrounding terrain is developed on limestone bedrock and exhibits karst topography due to dissolution of the limestone by ground water, creating water-filled sinkholes. The Blue Hole was known to American Indians and was first recorded in history in 1761. Several similar blue holes are known to local residents. The Blue Hole that once was a tourist attraction is now off limits to the public. It is located on the grounds of Castalia Trout Club. It is to be distinguished from another hole similar in size and eerie bluish-green color. This latter hole is owned by the Castalia State Fish Hatchery operated by the Ohio Department of Natural Resources, Division of Wildlife and is open for public viewing.
Blue Lake (Otago)
Blue Lake is a small lake adjacent to the town of Saint Bathans in Central Otago, New Zealand. The lake is man-made, the result of sluicing operations that began in 1873 when John Ewing (1844–1922) formed the St.Bathans Channel Company, to mine the Kildare Hill Gold Claim in St Bathans. His company constructed a tailings channel and introduced hydraulic elevating to work the claim. As this work progressed the Kildare Hill Claim became the site of the deepest hydraulic elevating operation in the world, that would turn a 120-metre hill into a 68-metre hole. Work stopped in 1902 when there was insufficient fall in the tailings channel to carry away the tailings. By 1905 John Ewing was bankrupt as a result of poor investments in other locations. The Kildare Hill Claim was then taken up by the Scandinavian Water Race Company in that year. This company restarted operations and worked the claim until 1932, when it was finally abandoned due to the fear of undermining the town of St Bathans. Natural drainage from the surrounding hills filled the hole with water and created the present day lake. The Blue Lake is a key feature of modern-day St. Bathans and is used for swimming, fishing, bodyboarding, and kayaking.