Over the last 16 years the U.S. Navy has spent $706 million developing a futuristic-looking device that could remotely detect mines underwater.

The only problem? The device, known as the Remote Minehunting System, doesn’t work.

The failed program, detailed in a new report released by the Senate Armed Service Committee Thursday, started in the late 90s and has yielded only half the number of planned systems with the cost per unit doubling since the program began.

On paper, the mine hunting system is meant to be deployed from destroyers and littoral combat ships as sort of a bomb-sniffing dog for the ocean. The system would scan an area, possibly even out of the surface ship’s line-of-sight, and would communicate back the location of detected minefields.

In 2007, after one failed test aboard a destroyer, the Navy went back to the drawing board and in 2008 the system was still testing poorly. Despite the results, the Navy purchased another mine hunting system at around $13 million dollars.

According to the recent SASC report, however, the device still doesn’t function as it should. In 2013 the Government Accountability Office noted that “in spite of starting development the towed sonar couldn’t not detect certain mines, and falsely identified other objects as mines.”

As of 2015 the system still has issues communicating back to the ship when it’s out of certain ranges and the sonar on the device cannot quickly or consistently detect mines. The report cites an August 2015 memo from the director of the Pentagon’s Operation Test and Evaluation Office to the Under Secretary of Defense for Acquisition as saying there is “no performance data to date to suggest that the [Remote Minehunting System] will eventually achieve [its] requirements.”

Undersea mines have long been a part of naval warfare. In the wars of the 20th century, mines played a pivotal role in disrupting shipping and sea lanes. While no U.S. ships have struck a mine recently, it is unclear how many mines are deployed and where they might be located. Currently, the United States has a small, but nimble fleet of minesweeping ships that run as screens for the fleets and waterways they are assigned to protect.