Shark Attacks

Boats Are Not Always Safe

People with fertile imaginations or those who have seen the film Jaws may find themselves wondering whether a shark of large size really could attack a man on board a boat, or even sink that boat.  Some factual stories are stranger than fiction.

On the physiological and physical level, some observations seem to some to be of interest.  With regard to kinetics, we have seen that only certain species, capable of top speeds, are able to leap out of the water.  This therefore excludes the slow species or the overweight individuals, and even then it is difficult to imagine a cold-blooded fish, such as the shark, making spectacular leaps like those of the warm-blooded mammals, such as dolphins of the killer whales.  It is physically and physiologically possible for some sharks to shoot their mouths one or two meters above the surface, but some do not think they can get much higher and no evidence exists in this direction.  However, it is clear that a shark heading, even at a slow speed, for the hull of a boat can shatter it like a walnut.  This is often seen with killer whales or sperm whales, which are much heavier, but just imagine the kinetic energy that a 1000 kilo shark can contain, even going at only 10 knots.  If in addition this kinetic energy is transmitted onto a boat hull by means of the pointed snout of a Great White for example, this is equivalent to an impact of several tons per square centimeter.  No wooden or plastic hull can withstand such a "snoutbutt".

Though, the shark does have relative fragility on impact, owing to its lack of suspensor ligaments to the organs inside the abdominal cavity and on account of its cartilaginous, rather than bony, structure.  It is for these reasons that a shark taken out of the water is often doomed, even if it is returned to its natural element, particularly if it is heavy.  This is no doubt also where we must look to explain the effectiveness of blows aimed at sharks to make them flee - although this is ineffective against the larger specimens which nothing can stop.

The two species which most often attack boats are the Great White and the Mako.  The first is the heaviest of the sharks (up to 3000 kilos) and the second the fastest (around 50 km/h).  Both are armed with a pointed snout, as are the majority of the Lamniformes (see the Directory of Sharks).

Regarding the motivation for attacks on boats, Tricas and MacCosher put forward an attractive hypothesis in 1984, following experiments on the aptitude of Great White Sharks for choosing between dead and living prey.  Living animals give out a weak electric field, but one that is still sufficient to be detected by the ampullae of Lorenzini.  Therefore it is quite conceivable that sharks could be attracted by boats on account of the electrical equipment found on board, in the hull or on the outside (sonar, sounder, log, etc.).

In October 1960, a fishing vessel was working in False Bay near Cape Town, and the crew were bringing in the lines, on which many fish were caught.  A big shark then appeared, and began to circle the boat.  The skipper order a halt to the fishing and went below to start the engine.  However, one of his men did not follow orders and continued to fish and very soon caught another fish which he immediately pulled towards the boat.  Just as he was preparing to hoist it in over the side with a gaff, the shark swooped on the still struggling fish but missed it, and came crashing with incredible force into the boat's guardrail before falling back again and disappearing.

Although the lines were then brought in and the boat prepared to cast off, the shark reappeared to continue its menacing circling.  Suddenly it charged at great speed, fitting its jaws flush into the hull and making a hole of 45 centimeters, luckily above the waterline.  A large fragment of tooth (18 mm) was later recovered from the breach, and identified by experts as belonging to the upper jaw of a Great White Shark (known as Blue Pointer in the RSA).

Again in South Africa, in 1946 at Table Bay, a small boat was sunk by a shark, which was on the point of consuming its occupants when the latter were rescued from the brink of death by another boat.  Three other vessels were attacked in the same place in the same year, perhaps by the same shark which had acquired a conditioned reflex?

False Bay at the south of Cape is without doubt one of the places in the world where most attacks on boats are recorded.  In addition to the 1960 attack already mentioned, two took place in 1942 involving a 6.5 meter shark.  In 1948, another boat was almost sunk.  In 1958, a Great white Shark bit the propeller of a boat which was trawling in Plattenberg Bay.  In 1960, another was sunk in Saldanha Bay by a Great White, although it had to go away hungry since its shipwreck victims were rescued just in time.  in 1970, six boats were attacked by Great Whites or by their "cousin", the Mako.

In 1974, in one year alone, Danie Schoemann saw his boat attacked three times in False bay.  Different sharks were involved each time, since Schoemann always succeeded in hooking or killing his aggressor.  In all, he was attacked five times, probably a world record, to the point where we might wonder whether his boat exhibited particular characteristics such as the electrical equipment or electric fields that excite sharks' curiosity.

In most cases, however, the boats attacked were actually fishing at the time, and one cannot be too careful in these circumstances when big sharks are seen circling in the surrounding area.

Again in the RSA, in 1977, four fisherman went to sea ----