Complex sentence: He estimated that a force consisting of gunboats and barges that could be sailed or rowed, manned by sailors and those in the shipbuilding industries, could engage British landing parties in the shallow waters of the Bay.
Split into simpler sentences: He estimated that the force consist of gunboats and barges that could be sailed or rowed. It was thought that a force of this composition, manned by sailors and those in the shipbuilding industries, could engage British landing parties in the shallow waters of the Bay.