Join us in exploring the fascinating world of sharks — creatures that have lived on the planet for more than 450 million years. Discover how sharks behave in the sea, how they use their senses to hunt for and find food. Plus, we'll also be talking about where you might encounter a shark, how to avoid a shark attack and what to do if you feel threatened by one in the sea.
There is no other animal that inspires such a wealth of myths and terrifying stories. Nonetheless, this extraordinary predator, a majestic traveller of the world's seas, is in danger. Not just because of the film Jaws – which portrayed the shark as a carnivorous killer and encouraged the defamation of sharks – but also because of the unsustainable hunting practices of the Asian fishing market. Sharks are a protected species; they never attack humans without provocation or reason and indeed largely avoid contact with them.
The shark is a protected species and never attacks humans without reason
An underwater close encounter with a shark is guaranteed to leave you forever captivated. They are sometimes even fondly referred to as being kitten-like. Their graceful, confident movement, steel-gray exterior, and stunning form are enough to enchant anyone. What’s more, sharks are extremely timid, so encounters are rare, particularly in Europe, where most often we sail.
What are sharks?
The shark is classed as a “chondrichthyan” (cartilaginous fish) and there are over 500 species. Most of them only reach a length of about 1.5 metres; only 10 species grow to more than 4.5 metres. The longest sharks measure nearly 20 metres. The dreaded great white shark can grow to around 6 metres, though on rare occasion will reach 8 metres.
The basking shark, or whale shark, can grow up to 20 metres long but feeds only on plankton
As equally diverse as their size is their diet. The whale shark pictured above will feed only on plankton, but the more predatory species also enjoy tuna, mackerel, cephalopods, sea lions, seals, and even green sea turtles! Some cannibal sharks even have a taste for their own kind.
The shark is the apex predator of the entire marine ecosystem and plays a particularly important role in its balance. It regulates the overpopulation of certain species, scavenges carrion and preys on weaker marine life.
Most species have a torpedo-shaped body and an elongated snout, but the structure of the body varies by species. Slower species, which live near the seabed, can be flattened like rays. The shark’s skeleton is made up of cartilage; they also have sharp teeth and, surprisingly, scales, which create a rough exterior to their bodies.
Shark jaw
Superb senses
What makes the shark a near-perfect hunter? Here it’s useful to consider its perfectly developed senses. The shark brain is able to process a great deal of information and to learn. Remarkably, the different senses interact to enable perception on a number of different levels.
The sense of smell is considered the most perfect. Sharks can smell blood at a distance of 1 kilometre. How do sharks determine the distance and intensity of the smell? Some species cross the scent trail, verifying the direction and distance and thus adjusting their course. The nostrils are located on the underside of the snout and consist of a series of folds of skin sensitive to chemical compounds.
The shark brain is capable of processing large amounts of information and learning
Research has shown that by the time a shark reaches a distance of about 250 metres from its prey, other equally well-tuned shark senses – vibration perception and hearing – are involved. Do you know what the lateral line system is? It is a line of faint pores running lengthwise from head to toe, and is full of receptors that register the changes in pressure and vibration caused by a moving animal. In this way, the shark can follow its prey at a great distance.
Depending on the type of vibration, it can even determine whether the animal is injured and thus an easy catch. Sharks are particularly sensitive to atypical vibrations. They are also aided by acute hearing, especially of lower frequencies. Both of these senses also facilitate orientation and the tracking of sea currents.
Another of the senses, sight, helps the shark by the time it swims to within about 25 metres of its prey. Often, it will then approach and circle to find out what the object is.
Once in its immediate vicinity, the shark can use electroreception to gather information about the prey. Sharks can detect the bioelectric fields produced by their prey. These impulses are perceived by sharks using special sensors (the ampullae of Lorenzini) which are found on the head (these look like tiny pores). Can you guess which species has particularly effective detectors? Yes, it's the hammerhead shark. It has a large concentration of these ampullae on its flat head thanks to its expanded “snout”.
Hammerhead Shark
At the point of contact, taste and touch also come into play. Sharks have tactile receptors around the entire body, and are able to gather information on impact with an object or by means of glancing taps. Taste – in the mouth and in the oesophagus – is the last sense which is involved. If the shark is unable (for example, due to poor visibility) to find out what the animal is, it can simply taste it and then decide whether it is fit to eat.
A sinker peers into the mouth and esophagus of a lemon shark
How does a shark hunt?
Most sharks rely on speed and a lightning attack which give it the crucial element of surprise. Sharks reach an average speed of 35 to 56 km/h, and the blue shark or shortfin mako shark can even accelerate to an incredible 86 km/h. A strong tail fin helps them. Speed combines with stamina in their efforts to capture and kill.
The mako shark can accelerate up to 86 km/h
Despite these commonalities, sharks are extremely versatile, never relying on only one strategy; added to this is the fact that the strategy of each species is different. Some species, for example, have a higher body temperature than their aquatic surroundings, and can thus penetrate easily into colder waters. Other species can be very patient. They will swim with a shoal of fish for so long and so inconspicuously, copying their movements until the fish lower their guard: then they attack.
Most sharks attack from behind (biting the tail fin), but the great white shark prefers to attack from below and surprises its prey by attacking from the depths. This is fatal to dolphins whose perfect sonar operates in a forward direction. The great white shark can also observe its prey from the surface.
The white shark uses both hunting and surface observation
Where can you find sharks?
Given the great number of species, sharks can be found almost the whole world over. Do sharks live in Croatia? According to some sources, there are as many as 47 species of shark native to the Mediterranean Sea, but most are smaller species.
From time to time tourists are excited by news of sightings of larger species on the shores of the Adriatic coast or Italy, but these occasions are few and far between. Mostly they are spotted where the last colonies of Mediterranean seals survive, or in places where flocks of tuna still pass. The number of sharks in the Mediterranean is steadily decreasing as, unfortunately, stocks of tuna and swordfish dwindle.
The dreaded great white shark can be found mainly on the northeast coast of the USA and off California, South Africa, Southern Australia and Japan. Many other species make their home in the Red Sea and the Caribbean.
Most sharks live in the open sea and often at great depths. They approach the coast specifically when hunting prey. Most likely you will meet a shark where the sea bed drops steeply from the shallows, usually at a depth of 1.5 to 3 metres. Some species live near coral reefs.
The lagoon shark (also reef shark or whitetip shark) measures only about 1.5 m
More articles about the underwater world:
So what if a shark does threaten you at sea?
As we mentioned before, the shark (or, for that matter, any other marine animal) does not consider man to be a natural prey. And so it will not attack unless it feels threatened or for some reason it is made to think of you as its natural prey. Or if you impulsively try to attack him.
For sure, forget about the scenes from Hollywood movies where a muscular hero strikes a poor shark with his fist, and it swims away half-dead. This may not end well for you at all. And most importantly, it is completely unnecessary: in the first place, the shark really does not want to attack you.
The shark (or any other marine animal) does not consider humans as natural prey
3 tips on how to safely encounter a shark
Employ tried and tested advice from people who have spent their lives researching sharks. If a shark approaches, it is advisable to do the following three things:
- Adopt a vertical position ( "stand" in the water)
- Move your legs as little as possible
- Give the shark your attention: turn towards it
Why should one try to stand up rather than continuing to swim? Here, we draw on the research and experience of Dr. Erich Ritter and other “sharkologists”. The theory goes that sharks will maintain a greater distance to vertical figures than horizontal ones. The fact that you are avoiding appearing similar to the shape of a fish in this position is also significant.
The recommendation to move your legs as little as possible will help the shark to correctly ascertain that you are not a fish or any other natural prey. To a shark, feet might be suggestive of an animal's tail fin in terms of both the motion and pressure. And so it might have the desire to explore them, in some cases with its mouth. And this experience is certainly one you might want to forgot.
The last piece of advice derives from the fact that sharks are often attacked from the rear or below, so it is worth facing them to show that you are not a threat.
“There’s no such thing as a dangerous shark, but the situations we create underwater can be dangerous.“
And what to do if the shark gets really close?
When a shark is really curious and contact is inevitable, it is useful to call to mind the so-called FACE – GUIDE – PUSH – MOVE rules.
Maintain a position facing the shark and keep track of it (the rule of standing vertically to the shark still applies). If it is close at hand, try to guide it gently in another direction, or lightly push it. Sharks are curious and usually only want to find out who you are, so there is no need to panic (they are very sensitive to this feeling of panic and it will be a signal for them to remain on high alert).
If, despite your efforts, it continues moving towards you, you must start moving away. Sharks do not really know what humans are and if you start to approach them, they will consider you a predator rather than a prey.
If the shark is too curious, it is good to know the so-called FACE - GUIDE - PUSH - MOVE rule
And what it all else fails? There is one more strategy, and this is always the last resort. Gently (!) touch the shark’s gills. The shark will understand this signal, because sharks themselves, in life and death situations, will primarily attack the gills.
The author of this proven rule is Dr. Erich Ritter, the Swiss founder of SharkSchool™ and the author of a wealth of texts on sharks; he has devoted his life to shark research and diving.
What else is good to know?
Sharks behave in a specific manner before attacking. They will circle their prey, change speed, approach the prey and attempt to drive the intruder away from their territory. Some species will lift their snouts and bare their teeth, arch their backs (this ensures greater agility) and their pectoral fins will be lowered. By taking note of these behaviours and understanding them, we can easily prevent any unfortunate incidents.
A shark raises its snout when it attacks
Do sharks ever attack humans?
Compared to other animals, the incidence of shark attacks is extremely low. Moreover, attacks that end in a fatality are a negligible percentage. In fact, these attacks are the result of a shark’s curiosity and disorientation, and when a shark “tastes” human flesh, it will tend to retreat rather than trying to kill or eat it.
According to Shark Attack File, which monitors the number of attacks, there are about 70 to 100 attacks per year, but only about 5 of these ends in a fatality. Many more people are killed, for example, by hippos, farm animals or bees: these are actually the culprits that top the list of animal killers. And in the United States, for example, more people drown in one year than sharks worldwide have been responsible for deaths in the last two centuries.
In 2021, for example, 137 attacks were recorded worldwide, of which only 9 were fatal. None of these took place in Europe. More than half of the incidents occurred in Florida, USA and some in Australia, which also had the most fatal attacks. More than 51% of all attacks involve surfers, 39% swimmers and 4% people snorkelling or scuba diving. In the popular sailing destination Croatia, attacks are almost non-existent, with the most recent one being more than 10 years ago old and the last fatal one 50 years ago.
Significantly more worrying are the figures in reverse: humans kill up to 100 million sharks a year. It is estimated that up to 50 % are caught "by mistake" when fishing for other fish.
How can I prevent a shark attack?
- Do not swim when you are bleeding. Sharks can smell blood from a distance and the smell will attract them. Sharks should not really be interested in eating people, but it’s best not to experiment.
- Avoid swimming near fishermen or where there is likely to be bait or carrion.
- Keep an eye on the sea. If you are in a known shark habitat, do not go diving where fish shoal or where other predators might be hunting.
- Avoid swimming "towards the sun". You won't be able to see what is going on underwater. In addition, sharks approach with the sun behind them in order to gain this predatory advantage.
- Don't swim at night. Although some species are active during the day, most hunt at night.
- Avoid rough and murky water, as well as estuaries. Here, sharks are more likely to lose their orientation, may not be able to see so well and can therefore mistake you for their natural prey.
- Do not touch, provoke or feed sharks. The smell of food can provoke them, and they may feel the need to defend their territory if they feel threatened.
- Do not hinder a shark’s efforts to escape into open waters.
And what species of sharks can pose a threat?
Potentially dangerous species include the great white shark, the tiger shark and the bull shark. The blue shark, shortfin mako shark, lemon shark and the hammerhead can also be moderately dangerous. But there is no need to panic. Again, it is worth remembering that sharks are timid animals; they do not attack without reason or provocation.
Tiger shark
Interesting facts from the mysterious world of sharks
- What's the relationship like between dolphins and sharks? They can quite happily swim together and occasionally even hunt together. In order to avoid being attacked, dolphins will flock together. An interesting encounter between a flock of dolphins and a large shark has been observed on a number of occasions – just as the shark approaches, the flock of dolphins suddenly splits into 2 groups; they encircle the shark and then reunite. When the shark swims away, the flock loosens again. A group of dolphins can effectively repel a lone shark.
- Active sharks need a lot of oxygen. In order to achieve this intake, they must always keep moving so as not to suffocate. Therefore, it seems some species have difficulty breeding in captivity.
- Sharks, unlike fish, have no swim bladder. Its function is performed by a large, fatty liver, which ensures the lightening of the body.
- Sharks have an excellent tooth replacement system. The teeth grow in several parallel rows and, if they lose a tooth, the replacement tooth fills the free space.
- Sharks are attracted to metal objects. This is because metal in contact with seawater produces a galvanic voltage. As already mentioned, sharks can identify prey from their electrical impulses. By the way, a shark’s ampullae of Lorenzini are extremely sensitive, so the shark can detect the bioelectric field of a prey even when it is buried in the sand.
- Hunting sharks are not very sociable and most often hunt alone or in a small group; some species occasionally flock together.
- How do their prey deal with the threat of sharks? Fish, for example, group themselves into larger flocks; a tightly bunched flock can change direction quickly and disorient a shark. Some fish sink deep into the bottom of the sea and some remain there. Some animals have their own specific defenses – they may emit a repellent substance on contact, or protect themselves with prickles or a carapace; the swordfish, for example, has its "sword", which can cause nasty injuries for sharks.
Interesting bearded shark with hammerhead
There are still significant gaps in our understanding of shark behavior and its life remains shrouded in mystery. But one thing is for certain. The shark is the apex predator of our fragile marine world; as such it performs a vital role as regulator of this ecosystem. However, despite its fearsome reputation, it sometimes escapes the concern of environmentalists.
In addition to Dr. Ritter and Alessandro De Maddalena (an Italian researcher and the author of a number of books on sharks), other organisations have recently devoted themselves to the conservation of the shark. In this way, hopefully, this beautiful, majestic animal can continue to cruise the world's oceans and its health will be nurtured.
“I absolutely adore shortfin mako sharks. When I’m out in the open seas and, from the blue of the waters emerges this elegant shark with its unmistakable silver lustre, it's like getting an amazing gift from the ocean.“
Did you enjoy this glimpse into the captivating underwater world? Choose a yacht with us and this magical place up close. Being aboard a boat will give you access places where life beneath the surface is wonderfully rich and varied.
Are you planning a boat holiday? Write me or call me, I will be happy to help you
