I called this book The Three Seas because the schooners in the three short stories were destroyed by heavy seas. Now, no doubt it took more than three seas to completely wreck the vessels, but there is something notable about three seas. When I was a boy, there was a rock off the Tickle, just under the surface which would break in heavy sea. No boat would venture in or out while that prevailed. However, after the sea broke over the rock three times in succession it became calm or much smoother.
Old fishermen and sailors experienced the same at sea. Three big waves, then a smoother ocean surface. They advised one to 'wait for three seas'.