Ballast water was first recognized by the scientific community as a vector for transfer of potentially invasive marine species more than 30 years ago. It took a number of years, and acceptance that zebra mussels had reached the Great Lakes in the ballast water of ships arriving from the Black Sea, before the maritime industry generally acknowledged that they were part of the problem. Initially, high seas ballast water exchange was the only available means for removing potentially invasive species from the tanks. That methodology presented risks to the stability of the ship (and the safety of the crew), as illustrated by the near-loss of the car carrier Cougar Ace in 2006 in waters of the North Pacific Ocean just south of the Aleutian Chain.