er for up to 40 minutes. Blue whale's usually dive to around 490 feet, but can go deeper if need be. When swimming slowly, the whale rises at a shallow angle. He blows as soon as the head begins to brake the surface. The head disappears below the surface and a long expanse of the back rolls into view. The dorsal fin normally appears some time after the blow has dispersed and the head has disappeared. The dorsal fin is visible only briefly before the whale arches its back in preparation for the dive. Sometimes the whale arches its tail stock, but often simply sinks below the surface.
             The blue whale can accelerate to speeds of over 19 miles per hour when it is being chased, but usually he swims much slower. Adult whales rarely, if ever, breach clear of the water. Youngsters,
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