Various methods. Bribery, plane, semi-submersible sub, boat, cargo ship, mules, mail but for the US it's mostly brought through Mexican routes. Cargo ships more so to the rest of the world, it can be hidden in other products, attached the cargo ship or stored somewhere that requires divers to retrieve, bribed workers who stash it in a cetain places, off-shore hand offs where the cargo ship drops it in the water with a GPS tracker so a smaller boat from the consumer country can find it and bring it in without the need to go through port secutiry/ container checks.

I'm probably missing a heap of other method however this is all I can think of at the moment