not through cargo ships. through the mail. 100 grams is very easy to hide in regular mail pieces that customs lacks the time and ability to inspect. 100 grams of fentanyl = 5 kilograms of heroin. in addition to this, china supplies our southern narco state with all the precursors they need to mass manufacture fentanyl/meth and smuggle it into the US using mules and underground cross border tunnels. The drug war can't even make a dent in any of these methods and in fact, seems to be having an opposite effect as the drug market continues to grow every year, despite the feds best efforts.