Later Turtle Ships held some structural changes as opposed to earlier versions. For example, later iterations of the Turtle Ship had a higher bulwark height. This alteration in the design was made so that more bulwark slots could be added. In turn, these slots could be used for additional weaponry or ventilation for the vessel’s occupants. Early illustrations also show initial versions of the ship consisting of overlapping planks on the deck structure, while later depictions show the deck of the vessel covered with flush, hexagonal plates made of wood or iron. Nonetheless, in both earlier and later versions, the Turtle Ship was designed to be surprisingly fast, as it was both oar and sail-powered.