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The origin of Blue Hole dates back to an ice age about 15,000 years ago.
Enough sea water was frozen in glaciers during this time to lower sea level
more than 350 ft, exposing the limestones of Lighthouse Reef. Huge
subterranean caverns formed when fresh water flowed through the limestone
deposits. Since then, the roof of the cavern has collapsed to form the
sinkhole.
Made famous by a Jacques Cousteau`s 1970 Calypso expedition, Blue Hole is
one of the best known dive sites in Belize. It is a circular, deep
depression in the center of more than 75 sq miles of shallow, blue-green
water. Its diameter at the rim measures 1,045 ft, whereas its maximum depth
is 412 ft. Except for two narrow passages on the eastern and northern rims,
Blue Hole is completely rimmed by living coral.
For the advanced diver this site is well worth the trip. You should plan to
dive either the north or south side to a depth of 100-150 ft where the
shallowest cave features are found. Begin your dive by snorkeling to the
coral rim. This serves two purposes: first, it conserves air, and second, it
provides an opportunity to get everyone making the dive together before you
descend. Your no-decompression bottom time is short at the planned depths so
it is best to snorkel toward the center to Blue Hole, just beyond the
vertical wall, before descending.
A good way of maintaining your orientation during descent is to stay
reasonably close to the wall. As you descend, you will notice that the wall
crests between 40-55 ft and continues as a vertical cliff to a depth of
90-100 ft before receding at a 55° angle. The resulting overhang forms a
cavern ceiling from which hang stalactites more than 3 ft in diameter and up
to 20 ft in length. Also found adorning the ceiling are numerous dripstone
pillows. More than 50 ft below the crest of the ceiling, the cave floor is
riddled with a collection of fallen stalactites, muddy sediment and an
opening to a cave system. Surprisingly, the dimly lit walls of the cavern
are covered by a variety of filamentous green algae, boring sponges and
encrusting worms. Little other marine life appears present in the cavern,
but the walls above are covered with cornflake algae and isolated growths of
gorgonians. Sharks and turtles may be found here, but their presence in Blue
Hole is unpredictable.
Marine life in Blue Hole and on the broad muddy sand slope that surrounds it
is rather dismal, comparative to other sites in Belize. Algae and encrusting
sponges mantle the walls to depth. Scattered growths of unhealthy stony
coral rim the wall and occur scattered across the broad, muddy sand slope
between the wall and shallow reefs. Most corals are heavily encrusted by red
algae, hydroids and gorgonians. The only other conspicuous organisms here
are shaving brush and mermaid`s fan algae.
The most varied and lush marine life is found on the coral reefs that rim
the perimeter of Blue Hole. The reefs occur in only a few feet of water,
making them excellent for snorkeling. Stands of elkhorn, club finger and
shallow-water starlet corals, giant green anemones and arious urchins occupy
the shallow lagoon habitat.
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