ALAMEDA (KRON) — The U.S. Coast Guard has seized 12,000 pounds of cocaine from a semi-submersible marine vessel in the Eastern Pacific Ocean on July 18, according to the Coast Guard.

The Coast Guard said a crew from the Cutter Stratton from Alameda caught four suspected smugglers and seized 275 bales of cocaine from the vessel worth more than $181 million wholesale.

The 40-foot vessel was detected more than 200 miles south of Mexico, the Coast Guard said.

“Our success intercepting this drug-laden, self-propelled semi-submersible is a testament to the collaboration of our partner agencies, and demonstrates the importance of our increased presence in the Western Hemisphere,” said Vice Adm. Charles W. Ray, who is commander of the Pacific Area. “Every interception of these semi-submersibles disrupts transnational organized crime networks and helps increase security and stability in the Western Hemisphere.”

Although the Coast Guard removed 12,000 pounds aboard the ship, the crew said when they tried to tow the ship to shore as evidence, it sank–along with 4,000 pounds of the cocaine.

The Cutter Stratton caught 15 different drug smuggling attempts since April, according to the Coast Guard.

The July 18 seizure is the largest involving a semi-submersible in Coast Guard history, the Coast Guard said.