depth of the Small Strait varies from and is free from navigational changes in the fairway but strong and irregular tidal streams make navigation hazardous. There have been frequent shipwrecks in the vicinity of Perim, particularly in the Small Strait. The absence of fresh water on the island has always been one of the major difficulties impeding permanent settlement. Although there are occasional heavy rains, there may be stretches of eight months or more without rain; the long-term average rainfall (in 1821–1912) was about per year. Vegetation is very scarce. History The straits of Bab-el-Mandeb were probably witness to the earliest migrations of modern humans out of Africa roughly 60,000 years ago. At this time the oceans were much lower because so much water was frozen in Ice Age glaciers and the straits were much shallower or dry. Despite its sheltered natural harbour and strategic location at the entrance of the Red Sea, Perim was largely bypassed by written history until the middle of the 19th century, in good part because the bare, waterless island could not easily sustain life. As a result, only fishermen and pearl divers lived there seasonally, building reed huts with material brought from elsewhere. In 1513, Afonso de Albuquerque, as part of the Portuguese bid to seize control of the trade routes to the Red Sea and the Persian Gulf, attacked Aden near the entrance to the Red Sea but failed to capture the fortified city. Having failed in his main objective, he nonetheless sailed for the Red Sea. The Red Sea pilots of those days lived on an island close to Perim and one was secured by sending forward as a decoy an Indian-built ship. The passage of the first Portuguese ship through the Bab-el-Mandeb was the occasion for much ceremony. After having spent some time at the island of Kamaran in preparation for an attack on Jeddah that could not be carried out due to contrary winds, the fleet left Kamaran on its return journey. Perim, which Albuquerque named Vera Cruz, was inspected and pronounced unfit for a fortress due to lack of water. During the following years, the Portuguese tried several more times to conquer Aden and gain the mastery of the Red Sea, harassing shipping and battling the Egyptian Mamluk, then Ottoman navies, which gradually gained the upper hand. These actions as well as the sending of an annual fleet to