Diving in Media Luna: Exploring an Ancient Lake
by Richard Worfel
Publication date: 2002, updated 2008
Author's Note: At least once a year my family travels from
Antonio, Texas, to the center of San
Luis Potosi. Our objective is to relax and scuba dive in
the state's clear rivers and at an exceptional lake called La
Media Luna. I love this high plateau environment and its residents.
I hope this article will be my first of many discussing events,
cultures, tourist activities, and economic issues effecting
the ecology and economy of the Huasteca Region.
La Media Luna (the Half Moon Lake) is a thriving wetland of
considerable ecological diversity. The lake's warm water (constant
temperature of 28 - 32 degrees C) and visibility of 20 - 30
meters 365 days a year make it an ideal site for scuba diving,
especially dive training.
La Media Luna is located at the far western edge of what is
known as the Huasteca Region, a region generally known for outstanding
rafting, rock climbing, kayaking, and exploring sites off the
beaten path to ancient ruins. La Media Luna is nestled in the
high semi-arid plateau of the Sierra Madre Oriental Mountains
in the State of San Luis Potosi (SLP). The entire basin is often
referred to as the Rio Verde Valley (Green River Valley).
In prehistoric times the valley was an extensive lake covering
the plateau. Fossil records found in-and-around the lake reveals
that mastodons and other prehistoric creatures were frequent
visitors to the clear waters of La Media Luna. Based on artifacts
discovered in the lake, ancient indigenous ceremonies (perhaps
were performed as early as 800 BC.
Engineers have attempted to mechanically tap the clean water
but each attempt has failed. Today, concrete pedestals once
used to support huge pipes that carried pumped water from the
lake have been converted to picnic table legs (supports). The
overflow is now channeled by gravitation to more than 5,000
hectares of farmland for irrigation hence changing a mountain
desert-land into a citrus fruit and vegetable bonanza.
WHAT ABOUT A DIVE SHOP?
A dive shop in a high plateau isn't always an easy find. But,
at La Media Luna, there is a well equipped PADI dive shop only
six miles from the lake. It's located along the southeast corner
of Federal 70 and the road that leads to the lake.
They carry new equipment and can repair nearly anything you
need fixed. Rental equipment is available for all sizes. Air
is available for pick-up at almost any time of the day "the
air is good!"
The shop is run by Ossiel Marteniz and his father. One of
the first observations you make while in the shop is Ossiel's
father standing in a photo with Jacques Cousteau. Now these
guys have been around! Ossiel is a university graduate in Oceanography
and teaches a broad range of courses from basic open water to
tech and cave diving.
They will provide you with whatever you need for your dive
and will also take you to various other sites. Taking an initial
tour dive with Ossiel will guarantee you will not miss anything.
The dive shop also has two pools, one for training and one for
Both pools are supplied with water straight from La Media Luna
irrigation water. While at the shop, don't forget to ask about
their museum of artifacts and bones they have recovered from
the lake. Keep in mind that many of the best artifacts they
have recovered are maintained in Mexican museums including the
world class National Museum of Anthropology in Mexico City.
DIVING LA MEDIA LUNA
The lake's water is extraordinarily clear. The mineral content
is a little higher than most freshwater and this contributes
to a slight increase of positive buoyancy for divers. The lake
is fed by six ancient thermal karst springs at depths of 10
to 38 meters with a flow rate of 4.35m3/sec. There are at least
ten species of fish, most are native and several are endemic
to the area.
Most interesting is Cichlasoma bartoni, a cichlid, called the
"skunk fish" by locals because during it's mating
season it becomes a black fish with a white stripe along its
dorsal area. The bottom of the lake is covered by a thick layer
of detritus with several small patches of sand. The detritus
requires divers to dive with care, trying not to disturb the
bottom. If it is disturbed, the visibility in and around that
spring will become cloudy and will require 20 - 30 minutes to
clear up. If one spring does become disturbed the visibility
of areas around the other five springs remains clear.
The aquatic vegetation in the shallow waters consists mainly
of beds of water lilies. It's a fascinating experience to watch
the gases bubble to the surface from the underwater leaves of
the lilies as fish and invertebrates hide under and around the
From the parking lot, there is a well maintained boardwalk that
leads to the lake. At the end of the boardwalk is a large dock
that is used by divers as a starting point. One giant stride
and your in the warm water with about 10 meters of water below
you. As one dives along the west side of the lake at about 10
- 15 meters an ancient petrified underwater forest is exposed.
Huge trees, perhaps cypress, fell into the lake long before
man arrived and became petrified in the mineralized water. If
a diver wants to do some deep diving, the deepest spring is
38 meters (about 118 feet) down and is located about 50 meters
from the dock (lamp required). The water rushes out of the spring
at around 33 degrees C or warmer (that's somewhere in the
area of 92 degrees F).
Another exciting and unique dive experience is a small cave-like
opening along the southwest banks of the lake. It;s not really
a cave as we usually think of caves. The ceiling is made up
of surface plant roots. Openings through the ceiling allow light
to enter so you are never in the dark. The diver is only 3 to
5 meters deep while traveling through the cave-like tunnel.
At approximately 50 to 70 meters there is a huge cavern which
is usually attended by turtles.
LA MEDIA LUNA'S FUTURE
Over the past few years intense tourist activity has led to
severe degradation of the natural conditions surrounding the
lake. The lake itself has not yet been seriously damaged.
Luckily, the government, at all levels, has recently declared
the lake and its surrounding land a natural protected area.
They recognize that once the biodiversity is damaged, aquatic
biotypes are difficult to restore to their pre-impact conditions.
Plans are being developed for habitat monitoring and the impact
users of the lake have on the lake's fragile ecosystems. Thanks
to residents like Ossiel Martinez and officials at all government
levels, a firm decree to manage the new, "El Parque Estatal
Manantial de la Media Luna," is underway.
For more information about the dive shop, visit Buceomedialuna.com.
HOW TO GET THERE
The lake is easily accessible and within a day's drive from
the Texas border. We usually leave early in the morning to avoid
potential long lines at the border crossing in Laredo. The total
distance from the border is 550 miles. Before departing Nuevo
Laredo, exchange dollars for pesos and make sure you get some
small coins for use at the rest stops. We take Federal 85 south,
through Monterey until we get to Federal 70, Ciudad
Good restaurants are located along Federal 70 in the small
towns and villages. The road conditions are usually very good
but be prepared to pay several tolls. Also, have all travel
documents organized for a traffic check approximately 12 miles
south of the border. Once on Federal 70, drive west for about
80 miles until arriving at the small town of Rio Verde. Continue
west all the way through the town until a large sign is sighted
(about a mile outside of the town) on the south side of 70;
the sign points towards La Media Luna.
Don't expect to find a street sign with a name on it. From
Federal 70 turn south onto the marked gravel/dirt road (expect
some dust) and drive about 6 miles along the irrigation channel.
Normal cars can make the journey if one is careful about missing
potholes. Where the road divides, keep to the right that will
put you on the opposite side of the irrigation channel. This
road will take you directly to the lake. You may be stopped
and asked for an entrance fee (usually on weekends).
Sometimes the road to the lake is delayed by donkey or oxen
driven wagons carrying abundant quantities of tree-ripened oranges
and other harvests to the market. Hey, this is a good time to
pull-over and take in the sights of agriculture being practiced
as it was hundreds of years ago. If you're lucky, you may even
get an orange or two that fell out of wagons as they maneuvered
around the potholes. There are other ways of traveling to Rio
Verde but this is the easiest. A more scenic route is to take
Federal 180 from Brownsville but this route will add several
hours or more to your driving time.
WHERE TO EAT AND SLEEP
My family prefers to stay in rooms provided at the dive shop.
The rooms are extra clean and nice. One pleasant alternative
is to camp outside the shop next to one of the pools (only a
few dollars a night). Clean restrooms and warm showers are available
for the tent campers. This area is exceptionally secure. It's
easy to sleep 4-6 in a day room. Ossiel's family goes out of
their way to make you feel welcome during your stay. Hotels
in Rio Verde can be found online Buceomedialuna
There is another alternative. Divers are allowed to camp in
tents along the shores of La Media Luna. It's only $3 USD per
day. It's not as peaceful as camping at the shop but it works
out just fine if you want to do a late-night dive.
Rio Verde has plenty of restaurants. Their opening times are
not very consistent and you really do't know from day to day
what they will have to offer. One is sure to find a nice place
to eat around the city square or along Federal 70 that goes
through the town.
We always eat breakfast at the restaurant attached to the dive
shop. The breakfasts are great, especially the fresh pressed
orange juice. The coffee is rich and the eggs are prepared any
way you want them. The restaurant at the shop also offers lunch
and dinner menus and a buffet. For lunch we usually experiment
with different foods in town.
In town, our favorite restaurant is La Cabana, the food is
genuine and exceptionally good and the prices are reasonable.
La Cabana is located along the west end of Rio Verde along Federal
70. Now if you feel like an evening drink or dancing, there
is a Disco in town called the Calypso with an interesting atmosphere
for divers (hardhats and more).
Rich Worfel has a BS degree in environmental studies and a
MS in animal sciences. He is a PADI dive master and dedicated
birder. To Rich, traveling is the spice of life. While serving
for twenty-six years in the military, Rich traveled to four
continents and sixteen countries. Those travels were for work,
today’s are for adventure and discovery. He can be contacted
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