Diving Half Moon Lake
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. Although it sits 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 go diving. Whether you want to continue your dive training, gain more diving experience or just add a new experience to your dive log, Media Luna offers an unique experience to anyone willing to make the trek. 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.
The other interesting feature below water is the petrified trees along the west side of the lake. Most are merely tree trunks but they are massive in scale. It appears they once lined the banks of the lake but either fell or where forced into the water over time. These remains are now hard as rocks and smooth to the touch. There are 10 in all and provide for some superb abstract landscapes.
There is an abundance of vegetation throughout the lake and many small fish. The vegetation is interesting because it abruptly ends at a depth of 9-12 m (30-40 ft). Beyond that limit there is only sand and sediment which require divers to practice good buoyancy techniques to not reduce visibility. If the sediment gets stirred up, the visibility will become cloudy and requires 20 - 30 minutes to clears up. The underwater vegetation in the shallower waters consists mainly of beds of water lilies. It's a mesmerizing experience to watch as tiny gases bubbles stream upwards to the surface from these underwater fields.
Puente de Dios
About an hour and a half from Media Luna is Puente de Dios or ‘Bridge to God.’ This river and connected waterfall is another local swim/ dive site. Once you park, you will need to walk about 400 m (¼ mile) to get to the dive site. This may not seem far but it is a steep descent and more importantly a steep ascent on the way back up after your dive. There are porters that will carry your gear for tips so make sure and bring some pesos. The usual fee is 50 pesos ($5.00 US) and well worth every penny. Even not carrying your gear the hike up can be somewhat tiring so make sure and remove your wetsuit before ascending.
The dive area is fairly shallow 9 m (30 ft) but very clear. Because it is a river there is a stiff current on the surface so get below quickly. Also, make sure as you dive that you scour the river’s bottom. As mentioned, this is a local swimming hole and you might be presently surprised at what you find fallen from the pockets of careless swimmers.
There are a number of small caves or grottoes and some petrified logs but really the good scenery is above water. There is one interesting aspect however. You can swim into a certain part of the river under the waterfall called the "Blender." This is where the water from the waterfall comes into the shallow pool. As you move up into the churning waters, it will shoot you out into the lagoon and if you don't pay attention, you might loose your mask, regulator, or even tank so be careful.
Be warned: if you have a guide, they will want you to get out of your gear and out of the water several times and into tight caves perched on precarious rocks for photos. Be careful when they tell you to move around the rocks. There is a high possibility you will slip and fall and if you do, you will head down river and over the falls.
Media Luna is easily accessible and within a day's drive from the Texas border. Make sure and leave as early as possible if you plan on driving to avoid potential long lines at the crossing. The lake is roughly 8 hours south of the Texas border just outside Rio Verde. Before departing Nuevo Laredo, exchange dollars for pesos and make sure you get small coins for use at the rest stops along the way.
Head to Monterey on Federal 80 until you get to Federal 70, Ciudad Valles. Then drive west for about 130 km (80 miles) until arriving to Rio Verde. Continue west all the way through town until you see the sign (about a mile outside of town) on the south side of 70 that points towards Media Luna.
Turn south onto the dirt road and drive about 10 km (6 miles) along the irrigation channel. When the road divides, keep to the right which will put you on the opposite side of the irrigation channel. This road will take you directly to Media Luna. As you enter, you will need to pay the entrance fee of 20 pesos (about $2 USD).
Eating and Sleeping
Just up the road from Media Luna, right where Federal 70 and the dirt road meet is the most convenient hotel to stay at when diving Media Luna. The Buceo Media Luna hotel offers a hotel, dive shop, and restaurant all wrapped up together. The owner, Ossiel Martinez and his son Saul will gladly show you their dive shop, fill station, and even their museum. The dive shop is not fully stocked but does carry most accessories or save a dive type items. If you are in need of other equipment, you are better off getting it before you leave or making arrangements with Ossiel before you arrive. The fill station is very modern and can pump air as well as nitrox, and they say, they can even get helium for trimix if given enough notice. Considering the depth and size of the lake, the expense of trimix is not necessary.
The artifacts in Ossiel's museum represent what he and his son have found over the years at the bottom of Media Luna. During the prehistoric period, the valley was an extensive lake and fossil records reveal that mastodons and other prehistoric creatures were frequent visitors to the clear waters of Media Luna. Based on artifacts discovered, ancient indigenous ceremonies were preformed as early as 800 BCE. A large sample of these artifacts can be viewed including large mastodon skulls and many arrowheads as well as native indian artifacts. Make sure and stop by museum to get a sense of the culture that once surrounded and utilized Media Luna.
The hotel looks like it came off a Greek Island postcard. The exterior is white but the doors, curtains, and details are all blue. It is not a 4-star hotel but it it fits the lifestyle of most divers. The rooms are clean, the showers are hot, and the grounds are well maintained. There is also a nice size pool that is fed by the warm waters of Media Luna. The restaurant at the hotel leaves a lot to be desired and there are better options in Rio Verde. Most dishes are generic in nature and offer nothing of the region's true flavor. Rooms run from $25-$50 per night. Divers can also camp along the shores of Media Luna for only $3.00 USD per day.
Places of Interest
Media Luna and a great portion of the state of San Luis Potosi are located at the far western edge of the Huasteca Region. This area is known for its outstanding rafting, rock climbing, kayaking, and other forms of outdoor pursuits. There are many activities in the area so do your research before you head down.
Rio Verde: The town of Rio Verde has roughly 100,000 inhabitants and currently (2008) there is construction mangling the main interstate leading to Media Luna. The government is putting in a 4 lane modern highway to connect the gulf coast to Mexico City. This construction impedes road transportation on a regular basis. In fact, the main road has been completely removed while construction is under way. To illuminate the roads and more importantly the many potholes in the roads, local construction crews light smudge pots (buckets of flammable liquid) to provide light so cars and pedestrians can pass safely. In the city center is the Zocalo which is small but charming and is of course where the city's main cathedral is located. Both are worth a trip into town for lunch and an afternoon stroll.
Tamasopo Falls: a beautiful swimming hole a few kilometers outside the town of Tamasopo. With a waterfall about 30 m (100 ft) high and a myriad of streams cascading down the mountain, surrounded by tropical rain forest, this is truly a magnificent stop. Try to avoid weekends and holidays because it will be extremely busy with local activities.
Sotano de las Golindrinas: "The Cave of the Swallows" is the 4th deepest open pit in the world at 400 m (1,312 ft). It is located on the east side of the Sierra Madre Mountains from Rio Verde. It is home to tens of thousands of swallows that circle the opening every morning to get the altitude to fly out. Discovery channel also filmed base jumpers parachuting into its depths.