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Diving the 'drop off' at Clifton             First published in the 'Nassau Guardian'.
The vast majority of the Bahama Banks lie beneath the sea. Twelve thousand years ago, when the sea level was lower and during that period known as the Wisconsin Ice age, the whole area we know as the Bahama Banks was dry land. But now the sea has risen once again to give the Bahamas the greatest shallow water area suitable for reef development In the Caribbean.   

The majority of the banks are still covered with oolitic sand, and in many places the dynamic process of carbonate formation is continuing. Here and there, however, the coral has found a firm foundation and patch reefs have formed.

 It is these patch reefs, and the more substantial fringing reefs, that make the Bahamas famous in the world of SCUBA diving. Today the Bahamas has more diving operations, and more people come here to dive than to any other location in the Caribbean.

 Clearly the Bahamian reefs are one of our most beautiful natural resources and certainly they are of tremendous economic benefit to the Bahamas. This economic benefit will continue to increase in future years and so the reefs must be protected in every way possible.

The non-diver cannot really appreciate the beauty of the reef en­vironment and the diversity of its fauna. From the surface the reefs are merely brownish patches. Even when a water glass is used, a deep reef can only be seen in a bluish monochrome, and then the three-dimensional aspect of the reef is lost.

 Total appreciation of the undersea world can only be attained by SCUBA diving. Certainly many people can free dive a great distance down into the sea, but they only have time to release a spear, free an anchor or take the briefest glimpse at the reef around them.

 Recently I had the opportunity to explore one of the most beautiful and exciting reef areas close to Nassau. At the western tip of New Providence, shallow water extends only a short distance from the shore, a few hun­dred yards out the seafloor plunges down to the great depths of the Tongue of the Ocean in an almost vertical submarine cliff known to divers as the drop-off. This drop-off is found along the entire northern and western edge of New Providence, usually beginning at depths in excess of 100 feet. Here though, in the Clifton area, it starts its rapid descent into the depths at only  45 feet (15m).

In those areas where the drop-off is deep, coral growth is sparse for coral requires light for optimum growth. Its tissues contain microscopic green plants called algae that supply important nutrients to the coral. Without this light the plant cells will die and the coral will no longer be able to survive.  

I was one of a group of six divers towed out to the drop-off from the shore behind a small boat. When we could see the deep blue of the ocean dropping away beneath us we released the towline and swam down to the edge.

As we approached the bottom the coral hummocks began to take shape. Shoals of small fish divided before us and inquisitive damselfish came closer for a better look at these invaders of their watery domain.

The lip of the drop-off is covered with coral growths growing both upwards and outwards. This is an ideal place for corals to grow. A constant current brings along plankton upon which they feed. The water at this point is clear and free from sediment, flowing in from the vast depths of the Tongue of the Ocean. The only evidence of man’s works to be seen is the yards and yards of monofilament and stainless steel trace that festoons the reef in places, for when a sports-fisherman loses his line it remains for years on the reef – protected from the plastic-degrading effects of sunlight by the depth of the water. 

We checked our depth gauges and swam out over the edge until we could see nothing below us but the deep blue of very deep water. Looking back the edge of the drop-off is a spectacular sight. The growth along the edge becomes sparser with depth. We could probably see down more than 150 feet. At this depth the cliff is almost bare rock - only a few sponges and whip corals break the monotony. We were not going down there, however, for several reasons. Firstly because our air supply would be rapidly used up, and secondly because we would be exposing our­selves to several of the dangers of diving. A diver who stays down too deep and too long may suffer from “the bends”, a painful condition caused by bubbles of nitrogen in the blood. Nitrogen may also become narcotic at depth and cause over-confidence and euphoria. It is for these reasons and others that all divers should undergo a proper course of training before taking up the sport. Diving is like driving. If one follows the rules it can be very safe, but if one doesn’t it can be very dangerous. 

We continued down until we reached our maximum depth of 80 feet. Now we could look up at the coral cliff rising more than 30 feet above us. Huge shoals of fish were silhouetted against the sunlight streaming down from above. A solitary Spanish Mackerel lazily finned his way and a huge and curious barracuda inspected us from a distance of 15 feet.

The barracuda is an inquisitive fish; he will always approach a diver and may follow him for some considerable time, but will never come too close.  He always looks more menacing than he is because of his habit of opening and closing his mouth to continuously pass water over his gills. To the diver it always seems as if he is gnashing his teeth prior to a meal!

Such a place is fascinating not for the grandeur of the terrain, or the spectacular views of the teeming fish, but for the close-up sights animals and fishes that few people have seen. Here the soft corals -  Gorgonians and Sea Whips form strange shapes. Stiff Wire Coral juts out as much as six feet from the rock in single filaments no more than a few millimeters in diameter. Giant tube sponges are almost as large at these depths where no movement from the surface waves disturbs the constant caress of the ocean currents. Some of the corals are extraordinarily brittle. The shallow cups of Agaricia coral are incredibly thin and break at the slightest touch.

The fish too are largely different from those of the shallow reef. Here is the only habitat of the Black-capped Basslet, Gramma melacara. This little fish is almost identical in shape and behaviour with the closely related Royal Gramma of shallower reefs. Its colouration however, is totally different.  Described in the literature as magenta, it appears to be a brilliant blue with a black cap extending from the mouth to the end of the dorsal fin.

Within their narrow zone they are extremely populous. Every niche or crevice in the rock is hideaway of a Basslet when danger threatens. Like the Royal Gramma these fascinating little fish spend much of their lives swimming upside down beneath overhangs.

Occasionally the cliff is eroded to produce a cave. Seldom does such cave fail to harbour some interesting animal. The smaller crevices contain Crinoids, ancient relatives of the sea egg and starfish, their feathery arms taking tiny planktonic animals from the passing currents.

Deeper caves may contain the giant Spider Crabs whose legs may stretch three or four feet from one side to the other

The larger caverns often have a large population of fish and frequently provide homes for the big Groupers found on the drop-off. The fish congregate within the crevices and caves during the day and venture out onto the exposed reef at night when they largely feed.

The scarcity of black coral at Clifton disappointed me. Here and there could be seen small bushes, but nothing large enough for commercial use. The law prohibits the taking of black coral by SCUBA diving. Nevertheless many people have been collecting this fairly valuable commodity for use both in Nassau and for export. The large mature black coral ‘tree’ provides a habitat for many animals; sponges and molluscs especially that live in its branches. The taking of the black coral has thereby deprived these species of a suitable habitat.

A fairly uncommon sight, but one most likely, to be encountered by a diver on the drop-off, is the enormous Manta Ray. The wingtips of this flattened relative of the shark may stretch as much as 14 feet across. Usually the rays swim in pairs parallel to the edge of the drop-off. Despite their huge size they feed on tiny planktonic animals that they filter out of the water passing through their gills. 

On occasions while SCUBA diving I have tried to follow them and hitch a ride, for they are entirely harmless. However, although they appear to be moving very slowly, they are usually moving a lot faster than a diver with a cumbersome air tank on his back!  My dive was coming to its end. Glancing at my watch I could see that I only had a few more minutes to remain safely at this depth, so reluctantly I signaled to my “buddy” (a diver should never dive alone, but in a “buddy pair”) and we began our ascent to the boat. 

Although I had dived here before, I’m always excited by the diversity of the Clifton drop-off. On every dive there is the anticipation that some giant creature of the deep may emerge. I am always fulfilled by having been there, but at the same time disappointed that so few native Bahamians will ever have the chance to visit this great natural spectacle.

 

 

© R. Attrill 2006