Smuggling It is not unusual for a pet to be sent by air cargo from Columbia to New York, but last December's shipment of a 4-year-old sheep dog caught a New York Kennedy Airport Customs inspector's eye. The dog looked to be on its last legs, and there was an unusual lump on the side of its body. An X-ray and emergency surgery revealed the presence of 10 condoms tightly packed with five pounds of cocaine that had been surgically implanted in the dog's abdomen - yet another first for Customs in the war on drugs. When it comes to transporting drags, the methods used are only as limited as a smuggler's imagination. Kilo bricks of cocaine are routinely concealed beneath false bottoms of containers that hold poisonous snakes. 'You've got snakes that are 12 feet long,' says a United States Fish and Wildlife Service agent - and sometimes the drag is in the snake. 'Who's going to pull it out and feel it?' In 1994, United States Customs seized 204,391 pounds of cocaine, 559,286 pounds of marijuana and 2,577 pounds of heroin. Just how much actually flows into the country is anyone's guess. Some Customs officials estimate that only 10 percent of the drugs coming into the country are ever seized. In Miami, the District Attorney won't even prosecute small fry. 'It's got to be over five kilos of cocaine, above a kilo of heroin and more than 5,000 pounds of marijuana or it's not something that we're going to stop the presses on,' says Tom Cash, a retired agent. Given this deluge, one can only wonder if agents are ever confounded by some of the smuggling methods. 'There are things we haven't seen before,' says John McGhee, a Miami Customs special agent, 'but nothing really surprises us.' The dog was different from others in that