La Laguna Media Luna (Half Moon Lake)
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Media Luna or Half Moon Lake is located in the Mexican state of San Luis Potosí in the high semi-arid plateau of the Sierra Madre Oriental Mountains at an altitude of 982 m (3,222 ft). The lake’s warm water 28-32° C (85-88° F) and great visibility 20-30 m (60-100 ft) makes it a perfect place to continue your dive training, gain more diving experience or just to add a new experience to your dive log. And, because of its protected status as a national preserve, the thriving wetlands contain considerable biological diversity for the photographer and naturalist alike.The lake is fed by five different thermal springs with a flow rate of 4.35 m3/ second. The flow is so constant that the warm clear water is used for irrigation for over 5,000 hectares of farmland. As mentioned, these thermal vents give Media Luna a constant warm temperature, but because of the lake’s arid location, you can quickly chill upon surfacing with the slightest of breeze.

There is a well maintained boardwalk that leads to the lake from the parking lot and at the end of the boardwalk is a large dock that can be used by divers for entries and exits. There are also several large picnic tables with grills where you can store belongings, prepare lunch or just relax between dives. The lake itself is of a moderate size with a maximum diameter of no more than 100 m (330 ft) or 25 hectares and an average depth of 9-12 m (30-40 ft) and a maximum depth of 34 m (110 feet). The deepest portion of the lake is in the center but that depth is not maintained throughout. Please remember, because it is spring water, the mineral content is higher than most freshwater sites which will increase your buoyancy so make sure and bring extra weight.

Two areas of interest underwater are the bog cave and the petrified trees. The cave is only 2-4 m (6-12 ft) deep but beautiful nonetheless. The cavern’s opening is disguised slightly by a fine dust of silt making it difficult to see. Once you get past the initial haze however, you will make out the cave’s opening and can continue back roughly 180 m (600 ft). The most stunning features of the cave are the shafts of light penetrating through cenote-style openings in the cave’s natural cover. This cover is made up of thick vegetation that gives the cavern its boggy texture. The openings provide light most of the way through but there is no light in the back of the cave so dive lights are needed. These shafts of light and their ghostly illumination make for striking, yet eerie photographs so bring your camera. To the left of the cave as you exit, there are 2 channels leading to the front of the lake. These channels are only .5-1.5 m (2-4 ft) deep but offer photographers a plethora of backdrops with adequate light for magnificent photographs. Be careful though, because of it shallow depths you might see one or two legs popping into your frame so be patient.
