SAN FRANCISCO — John Anderson, a plumber by trade and a beachcomber by passion, has been trolling the shores of the Olympic Peninsula in Washington State for more than three decades, and along the way has discovered almost every kind of flotsam one can imagine: toys, refrigerators, even the occasional message in a bottle.

But in recent months, Mr. Anderson has been making a new, and somewhat surprising, find: dozens of buoys marked with Japanese writing, set adrift, he believes, by last year’s catastrophic tsunami.

“That wave wiped out whole towns, I’m thinking just about anything could show up here,” said Mr. Anderson, 58, of Forks, Wash. “I’ve heard people talking about floating safes full of Japanese money.”

The tsunami — which struck after a massive offshore earthquake last March 11 — sent a wall of water sweeping across much of Japan’s eastern coastline and generated more than 20 million tons of debris, a jumbled mass of houses, cars, boats and belongings. And while it’s not clear what percentage of that wreckage was sucked back out to sea and what remains afloat, what is certain is that some of it is slowly making its way to American shores.