The starting age of using the dhows was clouded. Among all the different types of great sailing ships in the world, the dhow holds the longest continuous tradition of commercial seafaring. Arabian shipwrights and mariners practiced their professions. And after the tall-masted clippers were gone, and most of the world's commercial sailing fleets had been converted to engine power, the dhows continued their seasonal voyages, up until the 1950's, still powered by the wind. Dhows were mainly used for trading cargo, pearl diving, fishing and other more uses. Kuwait's fleet of dhows was one of the most impressive right until the development of the oil industry of Kuwait. Kuwait's economy depended mainly on three maritime activities: trading voyages, shipbuilding, and pearl diving.