At ports, enormous gantry cranes load and unload the containers from cargo ships. The largest container ships stretch over 1,300 feet from end to end. Tankers transport petrochemical or liquid cooking products such as olive oil. Tugs assist large ships into and away from berth. Straddle carriers stack and move containers from vessels in port. Oil tankers are among the largest vessels on the oceans. The most voluminous supertankers carry 440,000 metric tonnes. In Houston, petrochemical plants integrate with one of the largest ports in the world to supply America with fuel. The Port of Oakland handles trade from the Pacific Rim and delivers most of the ocean containers passing through Northern California to the United States. International cargo ships transport dry goods in bulk like this mountainous pile of sand in Port Newark. Large gantry cranes look like brontosauruses on the horizon. Mariners work 24 hours a day. From the vast open ocean, ships must all negotiate the same entryway into the Port of Houston. Movement in the port is regulated by strict security protocols. The scale of machinery in the port makes people look like ants. Some container ships posses their own cranes for loading and unloading cargo. The containers carried on truck beds also travel on barges and cargo ships. A ship's gangway connects two worlds. Crane operators hover high above the port to transfer cargo from vessels. Multiple containers stack like legos on board ships. Miles and miles of containers waiting for their next destination.