Simplicity in construction and repair are also basic requirements in the Arctic, where an emergency may make it necessary to repair or rebuild a damaged boat out of materials available nearby with the minimum of tools and under adverse weather conditions. The Eskimo has produced a boat construction that, as will be seen from the descriptions that follow, to a high degree meets this requirement. Exceptional seaworthiness is required, as most Arctic waters are subject to violent storms; the Arctic skin boats have been developed with forms and proportions to meet this condition. In this matter, the light and flexible hull structure gives a special advantage. The kayak, in its highest state of evolution and in skillful hands is perhaps the most seaworthy of all primitive small craft. The umiak is a close second, but of the two, the kayak is safer under all conditions of Arctic travel. The load-carrying capacity of skin boats has been mentioned. The Eskimo umiak is notable in this respect, exceeding the curragh and even craft produced by modern civilization. The umiak possesses this advantage because of its very light hull weight in combination with a nearly flat bottom and flaring sides. The resulting hull-form allows heavy loading with relatively little increase in draft, as the flaring sides cause the displacement to increase rapidly with the slightest increase in draft. Though a similar form exists in the lumberman's drive boat, the greater hull weight of this type makes it inferior to the umiak. Light draft when loaded has very definite advantages in the Arctic, for it allows loading and unloading on the beach or afloat, and allows the boat to be beached at points where this would not be possible with a deeper hull. The light draft also makes the umiak easy to propel manually.