Swift Keel (Civ6)/Civilopedia

As time passed in the salt sea after construction, the hull of a ship became fouled with marine life (notably, barnacles and shipworms) and suffered rot and corrosion. All of which slowed it considerably, and the hull became less streamlined and sturdy. Although various remedies had been tried over the centuries, it was not until the use of copper sheathing was pioneered and developed by the Royal Navy in the mid-18th century that a "cure" was found (although the American Revolution slowed the refitting). It proved a boon to naval raiders, who found it challenging to find a place to scrape and clean their hull. Thus, British-built raiders such as the copper-sheathed CSS Alabama, Florida and Shenandoah were both fast and able to remain at sea for long-periods.