As with other forms of travel, much water-based travel first developed for utility purposes, primarily trade, before emerging as forms of travel for tourism. Various different types of craft were developed to cross stretches of river, lake and sea, with water courses being the highways of the past. Tourists, like other travellers, used ferries and made use of major trade routes along European rivers, across the Atlantic and further afield to Africa, Asia and Australasia. Exploration of rivers was an essential part of the romantic period of the Grand Tour. In turn, travel across oceans became more appealing as sailing ships developed. However, early sea voyages were fraught with hazards and primarily undertaken by wealthy travellers intent on exploring new continents, partly on business and partly for adventure. Over time, voyages became safer as ship designs improved and in some cases vessels designed primarily with the tourist in mind were developed.