Shark attacks on humans are rare, and often occur when sharks mistake a surfboard for the outline of a prey item. Similarly, in the following attack the kayak may have resembled something edible:
On April 12th, 2012, twenty-seven year old Michael Demasi was enjoying the late afternoon in a small kayak on tranquil Dolphin Bay, South Australia, unaware of the great white shark below. Unexpectedly, and typical of great whites, the shark came up undetected from the depths and lunged, biting the kayak and piercing Michael's thigh.
What Michael did next might have saved his life, although unwittingly on his part.
Still not aware that his kayak had been attacked by a shark and believing he had run the kayak onto rocks, Michael took the time to grab his sunglasses before jumping into the water.
Finding neither rocks nor an underwater shoal that might have damaged his kayak, when Micheal surfaced from his bailout he finally noticed the shark - which fortunately didn't seem to notice him - as it used the kayak "like a chew toy".
Meanwhile his friend, 19 year old Elise Lavers, who had witnessed the entire event, raced towards Michael in her own kayak and was able to tow him to the safety of shore. Once there, and having determined that Michael's wounds were not serious they began to see humor in the situation and laughed as the shark continued to investigate the empty kayak. (Adelaide Now)
The shark may have mistaken the kayak for a dolphin or other prey species, since it did not first explore it closely or bump it as they are known to do when they are deciding if an object is edible. Sharks in general, but especially great whites, are thought to be somewhat intelligent, at least for a fish.
The ReefQuest Centre for Shark Research, in discussing the intelligence of sharks points out that while it can be fatal to us, most unprovoked attacks are exploratory when not a mistake - sharks chomp on humans occasionally, then spit us out before swimming off. In terms of shark survival, their ability to explore, sample and learn is evidence of adaptive intelligence:
The ability to explore novel objects and to learn which are edible and which are potentially harmful may lead to a richer, more varied, and therefore more reliable diet. Because reproductive success in sharks is directly related to feeding success - with better fed individuals generally attaining maturity at an earlier age and having larger litters of bigger pups, which are themselves better able to survive than smaller pups - being better able to be feed and avoid danger can be expected to result in greater genetic representation in future generations.
The Florida Museum of Natural History sums up the risk of any type of attack this way:
Shark attack is a potential danger that must be acknowledged by anyone that frequents marine waters, but it should be kept in perspective. Bees, wasps and snakes are responsible for far more fatalities each year. In the United States deaths occur up to 30 more times from lighting strikes per year, than from shark attacks per year. For most people, any shark-human interaction is likely to occur while swimming or surfing in nearshore waters. From a statistical standpoint the chances of dying in this area are markedly higher from many other causes (such as drowning and cardiac arrest) than from shark attack. Many more people are injured and killed on land while driving to and from the beach than by sharks in the water. Shark attack trauma is also less common than such beach-related injuries as spinal damage, dehydration, jellyfish and stingray stings and sunburn. Indeed, many more sutures are expended on sea shell lacerations of the feet than on shark bites!
Nevertheless, shark attack is a hazard that must be considered by anyone entering the marine domain. As in any recreational activity, a participant must acknowledge that certain risks are part of the sport: jogging offers shin splints, camping brings ticks and mosquitoes, tennis may result in sprained ankles, and so on. Beach recreation has its inherent risks as well, and shark attack is simply one of many that must be considered before entering the water. Most people agree, however, that the extremely slim chance of even encountering a shark - much less being bitten - does not weigh heavy in their decision-making.
Luckily for Michael Demasi, it looks like this shark was more interested in the kayak than it was in him - and possibly it was still toying with the kayak in order to learn the difference between it and the shark's usual prey.
Fortunately, the best available research tells us that this shark is unlikely to make the same mistake again.