Semi-submarines, which operate 99 percent below water, are being targeted by Congress as a way to deter drug smuggling, the Tampa Tribune reported June 27.

In fact, lawmakers are considering legislation making it a crime to be onboard a semi-submarine, even if no drugs are found. U.S. officials have seized five of the vessels since 2006; the latest was more than 50 feet long and loaded with six to eight tons of cocaine when spotted off the Ecuador-Colombia shoreline in the Pacific Ocean.

One official dubbed the vessels "floating coffins" crewed by four or five Colombian or Mexican fishermen who get paid about $30,000 to make the dangerous journey smuggling drugs to the U.S. The vessels usually have no toilets or even room to stand up, and are poorly ventilated. 

"These guys are just expendable," said Mary Mills, a federal public defender. "These guys in Colombia that are sending them, they don't care if they live or die."

Experts say that the semi-subs being used by drug cartels are becoming more sophisticated, costing about $500,000 each. They are equipped with scuttle valves that can be opened to sink the vessels if the sub is spotted by authorities.