Having the biggest economy as well as having unmatched cultural influence in the world makes the United States a very appealing destination. In fact, if the number of air passengers is anything to go by the United States tops the charts at 796 million air-line passengers above that of China’s 668 million. 124 million (15.6%) of these flights come in from outside of the US.

The human mind isn’t very good at picturing anything that amounts to millions. To get an idea of how many passengers 124 million is, imaging one person being a drop of water: that would amount to 6,500 litres of water. That’s enough to fill more than 80 bathtubs! It’s more than 8½ Jacuzzis. That’s a lot of water, and it’s a lot of people carrying a lot of stuff, some of which contains contraband.

Contraband is any item or substance that the government of a country does not want to get into its borders. These can include the obvious: recreational drugs and firearms, to the not-so-obvious: fresh fruit and vegetables and merchandise (including gold) purchased in specific counties. It’s the task of Homeland Security to prevent these millions of people from smuggling contraband into the country using every tool available to them.

Thursdays at 7 p.m. on National Geographic (ch 220) from March 12^th