Watercolour.
John Steven Dews born in 1949 is today seen as the preeminent marine artist of his generation. He receives highly paid commissions all over the world and is noted for his photographic detail of historic marine scenes and battles. For example, his large scale oil "The Capture of USS Chesapeake, 1st June 1813" (shown below). As an experienced sailor he is able to capture exact elements of the sea and sailing vessels, their rigging and highly realistic and expansive marine scenes. [And as a former watch leader myself on a square-rigged barque around The Canaries, and Transatlantic schooner skipper, I can appreciate such a seascape's realism and skill]