The blacktip reef shark (Carcharhinus melanopterus) is a common shark found in the tropical waters of the Indo-Pacific. Their bodies are streamlined, making them powerful swimmers, and—as the name suggests—the tips of their fins are black. They usually inhabit shallow waters and are very curious as a species. They will often approach divers to investigate, which has led to numerous attacks, giving the species a bad reputation. However, as with all sharks, the odds of being attacked by one are still extremely low.

(Source)

The whale shark (Rhincodon typus) is a graceful, slow-moving giant and the largest fish in the world. At 1.5 m wide, its mouth is large enough to fit a human inside, but it is a harmless filter feeder that eats only plankton and small fish. Accounts of these giants describe sightings of individuals up to 20 m in length.
To obtain the huge amount of food it needs, it sucks water into its mouth and pumps it out over its gills, where particles of food become trapped by bony projections called gill rakers and are later swallowed. This shark has the thickest skin of any animal, at up to 10 cm thick. Prominent ridges run the length of its body, and it has a large, sickle-shaped tail. The pattern of white spots on its back is unique to each fish, enabling scientists, through analysis of photographs, to identify individuals. While little is known of their ocean trabels, satellite tagging has shown that some whale sharks migrate across entire oceans. Whale shark eggs hatch inside the mother, and she gives birth to live young that reach up to 60 cm in length.
Every year, around April, whale sharks migrate to Ningaloo Reef off northwestern Australia for a plankton feast. The plankton explosion results from a simultaneous mass spawning of the reef’s corals, possibly triggered by the full moon.
Whale sharks are killed for their meat and fins (used in soup), although they are legally protected in some countries. 

Photo © Ken Knezick & Erik Schlögl

Along with the seven other known species of hammerhead sharks, the scalloped hammerhead (Sphyrna lewini) has a strange, flattened, T-shaped head. In this species, the front of the head has three notches, which produces the scalloped shape from which it takes its name. The eyes are located at the sides of the head. Hunting near the seabed, the shark swings its head from side to side, looking for prey such as fish, other sharks, octopus, and crustaceans, and using sensory pits on its head to detect the electrical fields of buried prey such as rays. The head may also function as an airfoil, giving the shark lift and helping it to twist and turn as it chases its prey.

Scalloped hammerheads may be seen in large shoals of over one hundred individuals. They give birth to live young in shallow bays and estuaries, where the skin of the young darkens to give protection against sunlight.

(Photo source)

Shark ‘Rescues’ Man Lost at Sea:
A 41-year-old policeman from the Pacific Island of Maiana found himself lost at sea with his brother-in-law, in what was supposed to be a two-hour boat ride. The two men — 41-year-old Toakai Teitoi and 52-year-old Lelu Falaile — started on May 27 with intentions of boating from Kiribati to Maiana. They stopped to fish along the way, slept overnight and awoke in the morning to find they had drifted out of sight of Maiana and were out of fuel. They had food, but no water. Without water or rescue, Falaile’s health failed and he died on July 4.

Teitoi buried his brother at sea and the very next day, a rainstorm that lasted several days allowed Teitoi to fill two 5-gallon containers with water. But weeks continued without incident or resuce. And then on Sept. 11, Teitoi was curled up in the shade under a covered area in the bow of the boat, when he heard a scratching sound on the hull. A shark was bumping against the boat. When the shark had Teitoi’s attention, it swam off.

“He was guiding me to a fishing boat. I looked up and there was the stern of a ship and I could see crew with binoculars looking at me,” Teitoi said.

The boat, the Marshalls 203, rescued Teitoi after 106 days at sea.

(Source)

Sharks are color blind, new research suggests, with the toothy predators likely forever seeing the world in black and white.

The study, published in the latest Royal Society Biology Letters, is the first to investigate the genetic basis and spectral tuning of the shark visual system.

The ramifications could be huge, helping to save both sharks and people.

“The work will have a major influence on human interactions with sharks,” co-author Nathan Hart, a research associate professor at the University of Western Australia’s School of Animal Biology and The Oceans Institute, told Discovery News.

(Read more on the implications for sharks and humans alike)

The open-ocean surface water can become impoverished, as nutrients are constantly absorbed by phytoplankton and fall with detritus to the sea floor. Nutrient-rich water can be restored to the surface on a large scale by vertical ocean currents in a process called upwelling. Near land, coastal upwelling is caused by surface currents, such as the Humboldt Current off South America. In the equatorial waters of the Pacific and Atlantic, mid-ocean upwelling occurs when water masses are driven north and south by the trade winds, and cooler, nutrient-rich water rises to take their place. Polar upwelling can happen where winter storms cause intense water movement. When upwelling occurs and there is sufficient sunlight, phytoplankton multiplies rapidly to support a vast number or organisms, creating the most productive ocean waters in the world.

Where there is upwelling, large numbers of small fish gather to feed on the plankton. They, in turn, attract larger predators like these copper sharks feeding on sardines off the coast of South Africa.

Cartilaginous Fish - Class Chondrichthyes

They have a skeleton made of cartilage, movable jaws, and their mouths are situated under their heads. Sharks, skates, rays, and chimaeras all fall into this class of fish. Pictured is a round stingray, most often seen in summer, when they move inshore into inlets and bays to forage for invertebrates among seagrass and bask in the warm-water shallows.

Afraid of sharks? Well, if you think a great white is cause for concern, you’re lucky you didn’t live in the Cenozoic Era. This monstrous jaw belonged to C. megalodon, a prehistoric predator that makes a whale shark look like a puny little thing. Most experts agree that it was over 16 meters (52ft) long, and could have reached a maximum length of 20 meters (66ft). This is not a shark to disrespect.

Photo taken from here.

(via )