A Ravel of Waters, by Geoffrey Jenkins, is an adventure novel published by William Collins as a hardcover in 1981. The edition that caught my eye is the 1982 mass market paperback published by Fontana. They had me at the golden sails. The artist: Chris Foss.
The first sentence:
Windeater. That should have been her name.Geoffrey Jenkins was a contemporary of Alistair MacLean and Desmond Bagley. His stories are very much adventure. At its best his work is a notch or two below the genre’s elite; at its worst, bumpy.