Ocean Watch

"Rare giant sharks under glass," said the headline, and beneath it was a picture of two sharks.

Sharks in a tank might not sound remarkable, but this isn't your average tank and these aren't your average sharks. The tank's acrylic window is the largest in the world, about 27 by 73 feet. And what people are viewing through this big window are the largest fish in the world, whale sharks.

The biggest whale sharks grow to about 60 feet long, but most adults are in the 40- to 50-foot range, about the size of our humpback whales. Also like humpbacks, whale sharks eat plankton, including shrimp, squid and schools of small fish, such as anchovies.

But the resemblance stops there. Whales are air-breathing mammals, and whale sharks are water-breathing fish. The word whale in whale shark refers only to its size.

Although this big fish is classified in the shark family, it doesn't resemble its cousins in either appearance or behavior. Whale sharks are deep blue with white spots and stripes over most of the body. Since these markings are unique to each shark, researchers use them to identify individuals.

These giant fish aren't as testy as most of their relatives, either. Whale sharks allow people ride on their backs and don't mind divers and snorkelers hovering around watching them eat.

Hitching rides on a whale shark, though, or even touching one is a no-no these days. Besides being rare in the first place, these creatures are overfished and in many countries are now strictly protected.

Whale sharks roam the world's tropical oceans and are occasionally seen in Hawaii. Boaters, fishermen and small-plane pilots sometimes see them off the lee shores of Oahu and the Big Island.

Several dive masters have told me stories about seeing whale sharks in Hawaii waters. When they accidentally find one, divers are first shocked and then thrilled.

Swimming with whale sharks is hit-and-miss here in Hawaii, but not in Australia. Whale sharks visit that country's western coast each March and April to feed on plankton blooms.

This area is now a national marine park, and whale-shark viewing there is strictly regulated. Small planes fly over the reef and radio the location of the feeding sharks to registered dive boats with a limited number of passengers. Each boat, one at a time, gets one hour with one shark.

Years ago, I was lucky enough to get to do this, and I remember vividly the fish's shimmering blue and white colors and its enormous mouth. Whale shark mouths are as wide as their heads and, when open, look like living tunnels.

Looking down the throat of a giant shark could be terrifying, but it was not. Our shark ignored us completely.

In researching Okinawa's whale sharks, I found another aquarium in Osaka and a third in Atlanta, all hosting healthy, long-lived whale sharks. In aquariums with large tanks, these big fish do well. One in Okinawa has been living there for nine years.

As wonderful as my personal whale shark encounter was, I'd still love to view them in an aquarium. In all three aquariums.

My must-see list just got longer.