Marine commerce is an area in which tide and current predictions are critical. In June 2002, these four marine cranes valued at $5 million cleared the Oakland Bridge in San Francisco Bay by approximately 6 feet. If you look carefully in the center of the image, you can see a shadowed figure between the crane and the bridge. This is one of the mariners standing on top of the crane and touching the bottom of the bridge as the barge passes beneath it.

Closeup of cranes passing under bridge

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