How the Panama Canal works shows why Trump wants it back so badly

Around 14,000 ships transit the Panama Canal annually. But the U.S. uses it more than any other nation with 40% of all U.S. container traffic, valued at $270 billion, traveling through the 50 mile stretch of water each year. Tensions in Panama are rising. The U.S. claims China has "influence and control" over the canal and that threat represents a "violation of the treaty" between the U.S. and Panama. A claim China denies. CNBC traveled to the Panama Canal to learn more.