The Sibuyan Sea is a small sea in the Philippines that separates the Visayas from the northern Philippine island of Luzon.. It is bounded by the island of Panay to the south, Mindoro to the west, Masbate to the east, and to the north Marinduque and the Bicol Peninsula of Luzon Island.
The Douglas sea scale, also called the "international sea and swell scale", was devised in 1921 by Captain H.P. Douglas, who later became vice admiral Sir Percy Douglas and hydrographer of the Royal Navy. Its purpose is to estimate the roughness of the sea for navigation.