An Underwater View

My exposure to and confrontations with Sharks started soon after I began Diving, in 1961. Since then, I have spent thousands of hours underwater all over the world and have seen more Sharks of every species than you can imagine. I have seen sharks, studied sharks (a 2 year study for U of Hawaii and the Honolulu Dive Council 1970/71), photographed sharks, run from sharks and defended myself from sharks.

I consider myself lucky ... I saw sharks very early in my diving career and learned how to see them. Many divers spend years in the water without seeing even one shark, but one fact has proven true over the years ... once a diver DOES see their first shark, they will see more sharks from then on. How and why this happens will become clear later on.

Contrary to popular belief, sharks are not predators ... they are scavengers; eating machines, not killing machines. Sharks would not have lasted, virtually unchanged biologically, for the tens of thousands of years they have if this were not true.

Predators generally lead relatively short lives. By definition, they must be aggressive and willing to fight for both territory and food. It doesn't take long for the average predator to start accumulating battle wounds which only help shorten their lives.

Scavengers, on the other hand, are meek by comparison, cautious when encountering something new and not willing to charge into any situation without carefully assessing any potential threat.

Sharks have developed a very impressive array of sensors with which they can detect the most subtle characteristics in their environment, but ... eyesight is not among them. The visual ability of a shark closely approximates that of a human underwater wearing a face mask. If the visibility is 60 feet to you, it's about the same for the shark. But, the shark only uses it's eyesight during the last few feet of it's approach .. and .. if it decides to bite something, it closes it's eyes a few feet from the target.

Consistent with being a scavenger, a shark's real sensory talents are in locating potential food at long distances.

Sharks have "ears" the full length of it's body, on both sides, and around it's head. These are similar to the Lateral Line found on all fish and is the dark stripe you see on the sides of fresh tuna.

These lines are actually a collection of small oil filled sacs of various sizes. Inside each sac is an array of hairlike strands (cillia) of different length. Being of different size, each cell or sac and it's corresponding cillia resonate at a different frequency allowing the shark to receive (hear) a wide variety of frequencies and to differentiate those discrete sounds from the background. Your $5000 stereo doesn't do as well, believe me.

These "ears" are so sensitive, they allow a shark to hear a diver from up to five miles away. Being curious, as well as cautious, sharks can accurately track a sound to within 2 degrees and will follow it to the source or until one of it's other sensors become more effective. So, it's a good bet that every time a diver goes into the water ... he/she is heard, approached and seen by a shark.

The shark's sense of smell is no less capable than it's hearing. Smell, or taste, is so highly developed in the shark that they can detect one drop of blood in twenty gallons of water. Since the Ocean is constantly in motion (in three dimensions simultaneously, by the way) sharks can follow a scent trail up-current from many miles away.

Another interesting sensor and one that is also highly developed, is the shark's ability to detect subtle changes in the ambient electical field. Observations prove that sick, injured or dying fish emit a different electrical constant than do healthy fish. This is one of Mother Nature's mysteries we have yet to unravel, but we've observed it consistently enough to know it's true.
Densly packed sensors around the shark's nose and mouth can detect these changes although they are so minute they can barely be measured by the most sophisticated equipment. These enable the shark to help locate their target without visual means and may help the shark classify the source as potential food, even in the dark.

Being scavengers, sharks find most of their food on or very near the water surface. Sick, injured or dying fish generally float since they lose control of their swim bladder. They also move spasmodically which puts small bursts of sporadic sound energy into the water. Sharks, detect these sounds and approach carefully to see if the sound is coming from something not only good to eat, but ready to be eaten and, out of habit, will generally search near the surface first.

Divers, on the other hand, are bottom dwellers. There's not much of interest at the surface or in mid-water for a diver. All the goodies are on the bottom.

So, here's Joe or Joanne diver, pulling themselves across the bottom by hand (divers don't swim much either) turning over rocks and looking for Spanish Doubloons or pretty pieces of coral with their back to the surface ... just where the shark probably is cruising.

If Joe or Joanne happens to look up at the surface, they will only see a light, shimmering expanse without much detail. Since sharks have light gray or white underbellies, they blend in perfectly with the diver's view of the surface and go unnoticed.
That's one reason most divers don't initially see sharks.

The other is that, even if the shark is near your level, it will approach and circle you at the very edge of visibility. If you can see 60 feet horizontally, the shark will take it's first look at you at 59 1/2 feet since it's visibility is about the same as yours. Cautious beggars, you can be sure.

What divers most often notice is only the flick of a shadow since the gray of the shark blends well with the darker bottom water when looking horizontally. Any surface wave action can cause similar effects and, again, the shark goes unnoticed.

In all but the rarest of instances, that's it!!! You've been heard, seen and evaluated as either non-food or too big to tackle. The shark resumes it's constant vigil and proceeds on it's way with you totally unaware of what just transpired.

Once a diver sees their first free swimming shark, however, the ball game changes totally. Now the diver's eyes and mind know what to look for and, wonder of wonders!!! ... more sharks are seen with every dive.

There is no reason to be any more wary of sharks than there is of a large dog on a dark street in a strange neighborhood. You would approach that dog, if you had to, as though you were the trespasser on his turf and make no threatening gestures. Sharks should be treated no differently. They are not "out to get" you, nor are they genetically programmed to attack you the instant they recognise you as non-ocean dwelling. But it IS the shark's territory. If in doubt, let them have it and return another day or just wait 30 minutes and they'll likely be gone.

Some good rules many seasoned divers adhere to is to, first, have one diver (you DO dive in pairs, right?) constantly be on watch .. head on a swivel type watch. One shark at a distance only means you pay a bit more attention, stay close to the bottom and move slowly and purposefully .. no unwasted motion, nor flailing around to make the shark any more curious than he is already.

If one or more additional sharks appear, clean up your job as quickly as you can and slowly depart the area to your boat or the shore, again, hugging the bottom.

If more than one shark starts nosing in closer, the best exit method is for one diver to provide locomotion by pulling accross the bottom while the other diver lies on top, back to back, so they can keep a watch on the sharks.

Sharks are amazing and beautiful ceatures. Even so, seeing one swimming freely does raise hackles on the back of your neck that haven't been there for several thousand years ... It's primordial. After seeing their first shark, I've known divers who have exited the water rapidly, offered their dive gear for sale and never made another dive ... it's THAT primordial.

But .. life without an occasional occurrence to raise your heart rate isn't really living, is it? It's only breathing.