5 pieces of tsunami debris found so far

Items ranging in size from a 164-foot shrimping vessel to a soccer ball have already made their way into North American waters following the March 2011 tsunami in Japan.

Environmentalists fear this is just the first wave of an estimated 1.5 million tons of debris that is in the ocean following the tsunami, much of which could land on U.S. shores.

Here's a look at some of the items that have already shown up, from biggest to smallest:

1. The 164-foot fishing vessel Ryou-Un Maru was in Hokkaido, Japan, and destined for the scrap heap when the tsunami dislodged it from its mooring. It drifted across the Pacific Ocean until the U.S. Coast Guard sank it in April 2012 in the Gulf of Alaska after determining it was a threat to shipping and the state's coastline.

2. Newport, Oregon, residents awoke Wednesday to find a 66-foot concrete and metal dock on the shore at Agate Beach along the central coast. The 165-ton dock was one of four that broke loose from the port of Misawa in the tsunami. Two other docks from Misawa are still missing.

3. A Harley-Davidson motorcycle was discovered inside a white container that washed up April 18 on Graham Island, off the coast of British Columbia, Canada. It was traced back to its owner in Japan by its license plate.

4. Cleanup workers near Craig, Alaska, in late March found a basketball with the words "Kesen chu," short for Kesennuma Chugakko or Kesennuma Middle School. Kesennuma is a major fishing port that was hit hard by the tsunami. Officials with the Marine Conservation Alliance in Juneau said the basketball was being packaged Thursday to be returned to Japan, along with a care package for students at the school still living in temporary housing.

5. David Baxter, a radar technician from Kasilof, Alaska, found a soccer ball in April 2012 on an Alaska island 110 miles south of the mainland. With the help of his wife, Yumi, who is Japanese and reached out to a Japanese reporter, the ball was reunited with its owner, a teenager who lost all his possession in the tsunami. A volleyball believed to be from Japan was also found on the trip.