 Because these methods are illegal, they are often dangerous.Would-be immigrants have been known to suffocate in shipping containers, boxcars, and trucks, sink in shipwrecks caused by unseaworthy vessels, die of dehydration or exposure during long walks without water.An official estimate puts the number of people who died in illegal crossings across the U.S.–Mexican border between 1998 and 2004 at 1,954 (see immigrant deaths along the U.S.-Mexico border).