Category Ask the Psychologist

(1) Sharks tend to target lone swimmers, so swim in a group.

(2) Leave the water immediately if you’re bleeding.

(3) Stay out of the water during the dawn and twilight hours, when sharks are on the prowl.

(4) Don’t wear shiny watch-bands or jewelry that sharks might mistake for dish scales.

(5) Avoid swimming in river mouths, areas between sandbars, or near drop-offs.

(6) Don’t swim near fishermen or diving seabirds. No reason to become shark bait!

(7) Wear a disguise. A company in Perth, Australia, designed a line of wet suits to make surfers, divers, and snorkelers appear less appetizing to sharks. The suit’s bold stripes mimic the coloration of dangerous marine creatures, such as sea snakes and lion-fish, which shakes avoid.

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Before you run screaming from the water, let’s get one thing clear: Shark attacks are incredibly rare. Far more people are injured by their toilets each year than by hungry shark. You have a 1 in 3,700,000 chance of being killed by a shark. And for every person who dies in the jaws of one of these fearsome fish, two millions sharks perish at the hands of humans.

But shark attacks do happen – an average of 19 attacks per year in the United States (and one fatal attack every two years). Researchers believe such attacks are typically a case of mistaken identity. A shark sees a swimmer’s hands and feet flashing in the murk and confuses them for the scale of a tasty fish. A surfer is a dead ringer for a sea lion or turtle when seen from below. Most shark attacks or humans are bump-and-runs – a quick taste of wet suit or surfboard or skin that tells the shark it has bitten the wrong animal. A bump from a little species might result in a few stitches. Bump-and-runs from great white sharks, which reach more than 20 feet (6 m) in length, can be much more serious.

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Marine biologists can’t always tell why pods of whales and dolphins – sometimes by the hundreds – will swim onto a beach and strand themselves in the surf; often dying en masse unless people manage to shove the behemoths back out to sea. Sometimes the whales are sick with pneumonia or some other illness. Sometimes they’ve suffered attacks from sharks or other whales species. Quirks in the Earth’s magnetic field – which whales follow as part of their biological navigation system – might also play a role. Mass strandings have been recorded as far back as 2,300 years ago, but some scientists speculate that strandings are on the rise today because of pollution and an increase in ocean noise caused by ship traffic and submarine sonar systems.

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With our two arms, two legs, and a dozen joints, humans have it easy when it comes to telling limb from limb. The octopus, on the other hand, has much more complicated body plan. Its eight boneless arms can form joints at any point, bending in all directions like cooked spaghetti noodles. And each arm bristles with hundreds of tooth-tipped suckers that stick to any fleshy surface. Imagine trying to untangle a string of holiday lights covered in glue. You’d think an octopus would spend every day just trying to keep its arms from tangling into one impossible knot, but these undersea wonders have two foolproof systems for keeping their limbs straight:

Smart legs: Each of the octopus’s eight arms has a mind of its own: a network of roughly 400,000 neurons that controls the arm without input from the animal’s main brain. These micro-brains help the arms work together rather than clump together.

Sucker-proof skin: Octopus skin excretes a special chemical. When the suckers brush against the creature’s other arms, they sense the chemical and automatically avoid latching on. The octopus can override this reflex if it wants to (say, it’s battling another octopus). Scientists think octopuses also rely on these chemicals to detect and identify each other.

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Because it’s home to billions of microscopic creatures called Pyrodinium bahamense that shine when disturbed – a phenomenon called bioluminescence. The best spot to see it in action is Laguna Grande, a bay on the northeastern corner of Puerto Rico. Every splash makes the water flash, and darting fish create lightning bolts in the deep.

Sea creatures glow primarily to communicate, defend themselves, and sometimes attract prey. In most parts of the ocean, especially the deeper areas, bioluminescence is the only kind of light ever seen.

Larger glowing denizens of the deep include jellyfish, many types of squid, flashlight fish, hatchetfish, dragonfish, and anglerfish. Other underwater light sources include ribbon worms, copepods, and at least one type of clam.

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Not only do coral reefs account for 25 percent of all life in the ocean, but they also serve as the sea’s early-warning system. The delicate relationship between corals and their algae roommates is vulnerable to the slightest changes in global climate and ocean health. A jump of even two degrees in water temperature sends the algae packing their bags, leaving the coral look. Pollution can poison the sensitive corals in their shallow habitats. When the corals go bad, the rest of the ocean could follow.

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