Ships during the period would carry fresh water in barrels in their holds -- barrels being relatively portable, manageable with sling and tackle when full and easily broken down into hoops and staves when drained. Ships would stop off and re-water whenever possible when they were near land, and watering places (streams or wells) were commonly added to navigational charts and rutters. In the period I study, British ships were starting to experiment with iron water tanks, but fresh water would still have to be carried out to the ship in barrels. It's estimated that about 9/10 of fresh water aboard ship would be used for soaking salt meat.