The five least dangerous sharks include the basking shark, the whale shark, the scalloped hammerhead, the horn shark and the zebra shark. Other sharks that are normally harmless, except when provoked, are the nursing and angel sharks.
Writing about the five sharks least dangerous to divers is considerably more difficult. Statistics exist on sharks that bite people, that’s news – sharks they don’t aren’t. There are more than 368 species of sharks; the nondangerous far outnumber dangerous.
For this article we eliminated nondangerous sharks divers never see (Megamouth, for instance). Then we eliminated sharks considered dangerous for any reason (except for one – more on that later) – Angels and Nurses, for example. Frequently seen by divers, these sharks are not ordinarily aggressive or dangerous. They do have sharp teeth and they do bite, however, if harassed. Thus, pulling on the tail of one of these sharks, cornering them or trying to feed them can lead to trouble.
We finally settled on the Basking Shark, Horn Shark, Scalloped Hammerhead, Whale Shark and Zebra Shark. The true title of this article, however, should be “Some of the Sharks Least Dangerous to Divers.” In truth, it would take a very large book to list those that pose little or no threat to us.
Two of the sharks we have chosen are huge. Growing to lengths of 41 feet, the Whale Shark (Rhincodon typus) is the largest fish in the sea. The Basking Shark (Cetorhinus maximus), known to reach 32 feet, is also a giant. Both of these sharks are harmless to humans, however, because, despite of their size, they are plankton eaters. They are sharks and they do have teeth – minute teeth. They are also totally nonaggressive, spending their time swimming near the surface of oceans around the globe with their mouths open.
Both sharks are unmistakable. Besides its size, the Whale Shark has a very distinctive pattern on its dark gray back, resembling nothing so much as rows of dominoes. Found in tropical seas, this enormous fish has small eyes, a flat head and a very wide mouth. It is the only member of its family.
The Basking Shark, with its small eyes and pointed snout, is very easy to identify. As you can see from the photograph, when opened, the mouth is absolutely humongous. The Basking Shark also has huge gill slits and very long pectoral fins. It is grayish brown to black on top, often marked with lighter patches. The underside is light and the tail is crescent shaped. According to Sharks of North American Waters, “It is found in subpolar and temperate seas throughout the world, occasionally straying into warmer seas in winter.” The Basking Shark is also the only member of its family.
The Horn Shark (Heterodontus francisci) is commonly seen by Southern California divers. Its sedentary, sluggish lifestyle, size (less than four feet long) and small teeth make it harmless to divers. It is nocturnal and during the day is usually “found resting with the head in a crevice” (Sharks of North American Waters).
The Horn Shark is brown with small black spots sprinkled randomly over the body. Adults may not have spots or they may be faded. The underside is pale yellow. The Horn Shark gets its name for a spine that extends from the middle of the leading edge of both dorsal fins. It has a “pig-like face” (Sharks in Question: The Smithsonian Answer Book) with a short, blunt snout and ridges above the eyes. It is commonly confused with the Swell Shark. Among the differences between the two sharks is that the Swell has a first dorsal fin considerably farther back on the body, above the pelvic fin. It has no “horns” and no ridges above the eyes.
The Horn Shark is a member of the Bullhead Shark family, which contains one genus and eight species.
The only shark included here that may result in angry letters is the Scalloped Hammerhead (Sphyrna lewini). A member of the family Sphyrnidae, it is one of nine species in its genus, Sphyrna. The Scalloped Hammerhead has been feared for decades, most probably because it looks so weird. The wide, hammer shaped head with eyes on the ends of the hammers is very exotic. And, the Scalloped’s close cousin, the Great Hammerhead, is considered dangerous. Divers, however, have been snorkeling and swimming with schooling Scalloped Hammerheads in the Sea of Cortez for more than three decades. In that time, these sharks have shown absolutely no interest in divers. In fact, the only way to get good photographs of Hammerheads is by free diving or using a rebreather – the sharks speed off into the blue when they hear or see divers’ bubbles. More recently, divers have encountered these sharks in various other areas, most notably off Costa Rica’s Cocos Island. Again, they have not proven the least bit dangerous.
The Scalloped Hammerhead has five notches and six scallops on its distinctive head. The body is gray on top; the underside is pale. The pectoral fins, the second dorsal and the caudal fin have black tips. The shark can grow to lengths of nearly 14 feet. The Great Hammerhead is larger; specimens 20 feet long have been reported. The Great Hammerhead’s head is nearly straight, the fins have no markings.
The last of our least dangerous sharks is the Zebra Shark (Stegostoma variuum). In the order Orectolobiformes, it is the only member of the Stegostomatidae (Variegated Shark) family. These heavybodied sharks live on or near the bottom and are found from the shallows down to about 90 feet. They are harmless to divers because they are very slow moving and have docile natures. In some areas they are handfed and seem to like being handled.
Zebra Sharks are so named because the young are dark brown with vertical stripes and white or yellow spots, reminiscent of a Zebra. These markings fade as the sharks mature. Adults are pale yellow or cream with dark brown spots. One of the most distinctive features of the Zebra Shark is its long tail – almost as long as its body. Since these sharks can grow to lengths of just more than 9 feet, their tails can be nearly 5 feet long. Zebras are found in the tropical Indo-West Pacific and the Red Sea.