Thirteen thousand years ago the northern Channel Islands—then fused into a single island—were separated from the mainland by five miles of open water. Clearly Arlington Springs man and his fellow islanders had boats capable of offshore travel.
Jon Erlandson of the University of Oregon has been excavating sites on these islands for three decades. He hasn’t found anything as old as Arlington Springs man, but he has found strong evidence that people who lived here slightly later, some 12,000 years ago, had a well-developed maritime culture, with points and blades that resemble older tools found on the Japanese islands and elsewhere on the Asian Pacific coast.
Erlandson says that the Channel Island inhabitants might have descended from people who traveled what he calls a kelp highway—a relatively continuous kelp-bed ecosystem flush with fish and marine mammals—from Asia to the Americas, perhaps with a long stopover in Beringia. “We know there were maritime peoples using boats in Japan 25,000 to 30,000 years ago. So I think you can make a logical argument that they may have continued northward, following the Pacific Rim to the Americas.”
Beaches along the Pacific coast still teem with elephant seals and sea lions, and it’s easy to imagine hunters in small boats moving swiftly down the coastline, feasting on the abundant meat. But imagination is no substitute for hard evidence, and as yet there is none. Sea levels are 300 to 400 feet higher than at the end of the last glacial maximum, which means that ancient coastal sites could lie under hundreds of feet of water and miles from the current shoreline.
https://www.nationalgeographic.com/magazine/2015/01/first-americans/