As a result of the tsunami in Japan, a huge floating debris field is due to wash up in Hawaii and the west coast states. Scientists are already are studying the problem and working to head off a marine crisis when the debris makes landfall in 2011. Some modest federal funding has been secured, but I am sure we will be hearing more about this threat in the coming months. See Inouye Steps Up With Money for Tsunami Debris Cleanup
Radioactive?