In the RN, a thing called a holystone was typically used, from the early days of sail through to the 20th Century. This was a large block of stone, usually sandstone, that was pushed back and forth over the deck. Before holystoning, the deck was covered in a mixture of sand and water. The stone was placed on top of this, and then scrubbed back and forth, abrading away the top layers of the wood, and forcing down any loose oakum. Once the holystoning was complete, the remaining detritus was washed away with hoses and buckets, or swept away with brooms and swabs. A swab was just the nautical term for a mop - they were either bought from a chandler, or made by the ship's carpenter. Saltwater was used throughout, yes.