This image shows the lake before its level was raised by a hydroelectric dam. Lake Cushman is near near Lilliwaup, where Otto's wife and daughters lived while he worked in Seattle.
The buildings in the background may be the Antlers Resort, which is shown in several of Otto's images.
There is also an Image 219 (219 - Idaho Bldg A.Y.P.E.) from the 1909 World's Fair held in Seattle, the Alaska Yukon Pacific Exposition. Perhaps Otto reused the image number because no one would be interested in an A.Y.P.E. card after the exposition ended.