A rare species of sponge found in the Red Sea and Indian Ocean has a rare distinction: It has levels of a metal that are thousands of times higher than ever seen in any other organism. And most of that metal is stored away by a type of bacteria that lives inside the sponge.

Sponges are filter feeders—they draw in water, filter out food and other solid bits, then shoot the water and solid particles back into the sea. Some contaminants can lodge inside them. Some studies have found high levels of arsenic, barium, and other toxic substances.

A more recent study looked at the species called Theonella conica. It’s found down the eastern coast of Africa. Up to 40 percent of its body weight consists of bacteria and other microscopic organisms, many of which have a symbiotic relationship with the sponge.

Over two decades, researchers collected specimens from Zanzibar, off the southeastern African coast, and the Gulf of Aqaba, at the northern tip of the Red Sea.

When they analyzed the sponges, the scientists found extremely high levels of molybdenum. The metal is important for the metabolism of people and other animals, but only at low levels. At high levels it’s toxic. So the metal may help protect the sponges from predators.

The element was concentrated in one of the species of bacteria inside the sponge. It changes the material into a harmless mineral, which is flushed back into the water—keeping the sponge safe from both predators and the toxic element.

The journey around Cape Horn, at the southern tip of South America, is one of the most treacherous in the world. The cape has claimed hundreds of ships and thousands of sailors. Not many commercial vessels make the journey today. But for sail-powered yachts, rounding the cape is a big attraction—like climbing Mount Everest.

Cape Horn is named for the home town of the Dutch navigator who described it, in 1616. It’s a small island that features a cliff a quarter of a mile high.

The cape is where the Atlantic and Pacific oceans meet. The confluence generates strong currents. Those currents are magnified by the contours of the ocean floor, which features many sunken islands.

The region is in the “Furious Fifties”—latitudes of more than 50 degrees south. Strong winds blow from west to east. Those are funneled by the mountains of South America and Antarctica. That creates a wind tunnel effect, so winds almost always blow at gale force. And they frequently top hurricane force, battering any ships that challenge the passage.

In addition, icebergs are common features, and storms bring heavy rain, hail, sleet, and snow. That all combines to make a journey around Cape Horn especially challenging.

The opening of the Panama Canal, in 1914, provided a safe shortcut between the east and west coasts of the Americas. But big tankers, naval vessels, cruise ships, and private yachts still round the cape—one of the most dangerous ocean voyages in the world.

The coconut crab is the 800-pound gorilla of many tropical beaches. Not only is it the biggest and strongest crab on land, it’ll eat just about anything—animal, vegetable, or even mineral.

Coconut crabs are found in tropical environments in the Indian and southwestern Pacific oceans. They hatch in the sea, where they float around for a few weeks. They then move ashore, where they live in the discarded shells of other creatures. The crabs lose the shells when they become adults. They stay close to the beach, but they don’t go back in the water; they have lungs instead of gills, so they drown if they stay underwater for long.

An adult coconut crab has a leg span of about three feet, and can weigh up to nine pounds. It has powerful claws that can crack open a coconut and scoop out the meat. It can even climb a tree to knock a coconut to the ground.

The crabs also have been seen to climb trees to attack seabirds. Most of their diet consists of fruits, seeds, and dead animals. They eat abandoned shells for their calcium. But they sometimes grab birds, rats, or even other crabs. And they steal many human artifacts, from pots and pans to firearms, so they’re also known as robber crabs.

Coconut crabs have been wiped out in some regions. They’re hunted for their meat, crowded out by human development, and damaged by higher sea level and warmer oceans. Some areas offer legal protection—a helping hand—or claw—for these giants of the beach.