The whaleman's rule of thumb was that, before diving, a whale blew once for each...

The whaleman's rule of thumb was that, before diving, a whale blew once for each minute it would spend underwater. Whalemen also knew that while underwater the whale continued at the same speed and in the same direction as it had been traveling before the dive. Thus, an experienced whaleman could calculate with remarkable precision where a submerged whale was likely to reappear.

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