The cave is in fact an ancient lava tube of the inactive volcano called Piton des Neiges and is about 12,000 years old. The depth (-33 m) can be explained due to the fact that the sea level at the time of formation was much lower then the current level. The total lenght of the cave is about 370 m of which 330 m is submerged.
|Survey of the Trou d'Eau on Réunion.|
The dive commences in a lake at a small underground beach. A 4 by 6 meter tunnel leads to some breakdown. After a light ascend the tunnel descends gradually (at 240° N). The sight becomes a bit hazy as you cross the barrier between sweet and salt water. At a depth of -33 m the tunnel becomes too small to continue, but the presence of eels suggest a connection with the ocean.
The following video of Dominique Debaralle & Sylvain was shot at February 28th 2012. They are currently doing some exploration in the cave. A true documentary will follow later.