There were certain items that all sailors — whether merchant, pirate, privateer, or Naval officer — could not sail without. These were the tools that were needed in order to navigate across the world's oceans. One of the most important was the sextant. Used to measure the angle of the sun or stars above the horizon, the sextant helped captains and navigators determine their latitude. Another important tool was the compass, which helped guide them in the direction they were headed. Without these tools, it would have been easy to miss land and sail completely off course, which could be devastating on a ship with limited stores of supplies.
Pirates also followed charts, which were maps drawn by cartographers or other individuals who'd sailed the same routes. The charts depicted specific areas of water and the coastal regions surrounding it, pointing out hazards and landmarks that could be used to assist in navigation. Given the complexity of high seas transport, it's little wonder that the navigator ranked as one of the most important crewmembers on a ship.