The only way to cross
Boats have carried passengers across stretches of water since they were first developed. Boats matured into ships, and masts and rigging were devised to use wind power to drive the ships along. Gradually, ships made longer and longer passages, along coasts and across seas and oceans. For even when there was an alternative land route, going by sea was usually quicker. Until railways arrived in the 1830s, land travel was limited to walking speed. Even when it relied on the wind, a sailing ship could better that.
Even so, sea travel was slow, uncomfortable and hazardous. People travelled as passengers only when they had to, for example if they were traders, ambassadors or soldiers. It was only in the eighteenth century that improvements in the build and rigs of ships meant a long sea passage could be undertaken with confidence. This period saw the beginnings of mass movements by sea, with thousands emigrating from Europe to the `new worlds` of the Americas and Australasia.