On any given weekend, the Cape Cod canal in Massachusetts is generally bustling with commercial and recreational vessels, river boats, and cruise ships. But that wasn't the case this past weekend. On Sunday, March 5, three endangered whale sightings closed the Cape Cod canal. Shipping traffic was temporarily marked off, to protect them from being hit. And although the canal has since reopened, it's still unclear how or why the whales swam through in the first place.

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