Virgin Islands National Park - The Rainbow Realm

Corals in all their varieties, shapes, and sizes are the very foundation for survival of a host of other animals and plants that live on the reef. For some, such as parrotfish, corals are a source of both food and protection. Crevices, overhands, and caves in the reefs allow the fish to hide from predators; for food the parrotfish eats algae growing on dead corals, which it takes with its sharp, parrotlike beak. In the process the fish crushes the limestone and converts it into fine sand, and so contributes to the building of the island's lovely white beaches.

The ideal way to explore this fascinating world is by donning face mask and fins or, for the more adventurous, scuba gear. Regardless of choice, entering this realm is a little like being an astronaut landing on a strange new planet. The strongest first impression is one of color -- astonishing, vivid colors of every hue. Your gaze is torn between the bright orange "antlers" of elkhorn coral; the green and yellow forms of brain corals; the white to yellow staghorn coral that lies in tangled masses on the bottom; the purple sea fans swaying gently in the undersea currents; and the brown pillar coral growing in tall, cylindrical columns whose soft, furry look belies their rocky hardness (the "fur" is actually the tentacles of thousands of coral polyps).

When you move closer, the color becomes even more astounding. Sponges with an incredible array of hues make their home among the corals. Intense red, orange, green, yellow, and blue forms of these simple animals can often be found growing within inches of each other. Adding to the chromatic explosion are the fish -- blue and green wrasses; red-striped squirrelfish; bright yellow juvenile tangs and the fluorescent blue adults; multicolored angelfish and butterflyfish. The variety is overwhelming.

And that is what usually makes the next-strongest impression on the novice reef visitor -- life. Teeming life. Swimming among or living amid the corals is an incredible richness of life-forms, plant and animal, vertebrate and invertebrate. Under a shelf of coral a spiny lobster may sit quietly, only its spiked antennae protruding and probing for food or signs of danger. Delicate fairy shrimp scavenge the nooks and crannies, looking for the leftover morsels of another's meal. Orange-spotted flamingo-tongue cowries and other equally colorful snails cling to sea fans and sea whips. Attached to the surfaces of star corals and brain corals are numerous tube worms topped with feathery plumes that sway in the current to capture plankton. The most common types are Christmas trees and feather dusters, both aptly named for their shapes.

And there is more. Black sea urchins are everywhere, their long, slender spines waving menacingly as though to warn that contact can be painful. A three-foot-long moray eel slithers snakelike past a brain coral. Despite an evil reputation, it presents no danger to divers or snorkelers if left undisturbed. The same is true of the octopus, a gentle, timid reef dweller that is rarely seen. A master at hiding, it can ooze its soft, fluid body into the most improbable crevices, emerging only to stalk its favorite prey -- such mollusks as conchs or whelks. Using its parrotlike beak, it can open or chip away the hardest of shells to get at the animal inside.

Although such creatures sometimes frighten newcomers to the reef, in reality few things here are harmful to humans. True, a person foolish enough to thrust a hand blindly into a dark crevice might be bitten by a moray eel, but such occurrences are rare. Nor is there much danger from sharks, since these predators of the open sea seldom venture into the shallows near shore.