Captain Finn Andersen discussing the geography of the Pacific Northwest
The northwest coast of North America properly begins at Cape Flattery. From there south, it is pretty much sandy, with out a lot of inlets and indentations other than the Columbia River. From there north, all the way to Alaska, there are many, many inlets, small islands, uncharted reefs, and it would have been really difficult for navigators to transit this area safely. It would require continuous sounding of the depths to make sure that they weren't going to run aground, and continuously fixing their positions, often using small boats to explore the indents and indentations along the coast, because it would have been unsafe to sail their ships into those, and if they did sail them in they might not have been able to get them back out because of such strong tides.