It looks like drug runners are going under the sea to move their illegal goods from one place to the next.
Coast Guard Alameda reported the bust because it happened in the Pacific Ocean and under their jurisdiction.
The semi-submarine is commonly referred to as an SPSS. It's not 100-percent submerged, but most of its bulk rides under the water line. Its low profile makes it hard to detect.
Often they have some kind of sink button so that drug-runners can put the sub on the ocean floor before the Coast Guard can get aboard.
This week's open ocean find is the second seizure in a week for the Dallas. Its crew also seized more than 5,000 pounds of cocaine off an 87-foot Mexican flagged fishing vessel. Coast Guard Alameda said the drugs were stored in a hidden compartment that was built into the fishing vessel's fuel tank.
The Dallas is a long way from home as it patrols the Pacific. It's 160 member crew are based in South Carolina. They carry out their missions from New England to South America via the Panama Canal.