Large ships that could be carrying invasive species into U.S. waters are the focus of a new review. A Coast Guard review is looking at the water ships take on for balance, then release near ports. The 12-year-old rule is meant to stop unwanted plants and animals from hitching a ride from one waterway to another. The Coast Guard says those species can damage fishing areas, waterways, and port communities. The review does not announce a rule change yet, but says treatment systems cost ships heavily upfront, but may prevent bigger damage over time.