Why Sharks are the Apex Predators of the Ocean.

It goes without saying that sharks are dangerous, scary, intimidating, intriguing, mysterious, amazing, and captivating animals. But when you really look at a shark, their physical characteristics, the way they move, eat, and hunt, you can see why they are all of those previously mentioned adjectives and more.
Let's take sharks' skin first. It is covered with thousands of dermal dentricles which are like tiny little pointed knifes that are in one direction. Not only does this increase their speed and fluidity while swimming it also makes them dangerous to touch. If touched in the opposite direction of these dentricles, a person or animal can get cut and start bleeding. (Best to make sure that if you touch a shark you move your hand in the direction of left to right to avoid getting hurt).
Second, have you ever noticed how all sharks (no matter what species) have a distinct horizontal division of color on their bodies. The top half, where a shark's dorsal fins are located is usually a gray, blue, dark blue or black color. The bottom half of a shark, which is where a shark's pectoral fins are located is usually white or cream colored. This is why: when you look up at a shark, (i.e. you're below a shark looking up at it), the sun and the clouds camouflage the shark's light underbelly. When looking down on a shark (i.e. you're above a shark looking down), a shark dark skin is camouflaged with the dark ocean. This genius skin-coloring allows a shark to swim in the ocean undetected and to make it harder for prey to distinguish them.
Next, let's take sharks' eyes. Sharks have excellent night vision and they never have to blink because the surrounding seawater clears their eyes from any harmful bacteria. But what is most intriguing, is that when a shark attacks it's prey a protective cover immediately covers their eyes so that if their prey thrashes around and it hits one of the sharks' eyes, a shark won't get hurt or go blind. This protective cover is called a nictitating membrane, and seeing as most sharks use a "thrashing around" method to kill their prey, sharks probably get hit in the eyes quite often. Just another example of what amazing creatures sharks are.
Next, let's take a sharks' mouth. Sharks have more than one layer of teeth, usually they have three. The first row is what you would see immediately because it is the one that is up front. The other two rows are hidden towards the back of a shark's jaw; and they push forward when the front-row-teeth fall out. Think of it as an insurance policy. Sharks lose their teeth constantly; seeing as they don't have hands, shark's teeth are their main means of killing and cutting into their prey. Over time, their teeth lose their sharpness and also become loose due to them having to hold down their prey to feed. So nature built a survival mechanism of keeping extra rows of freshly-sharpened, strong teeth in storge, so that when a shark does lose some of them, they're immediately replaced.
It is amazing how every part of a shark was created for them to survive in a variety of situations and circumstances. They are so adequately equipped with whatever they need that it is hard not to admit that they are amazing creatures that should be respected. Their efficiency and precision explains why sharks outlasted the dinosaurs and why they are the rulers of the seas.
Here are pictures that show (a) shark's skin up close, the dentricles, (b) shark's eye being covered by the nictitating membrane, (c) shark's coloring, and (d) the three rows of teeth.