Until the 1820s, oceangoing ships carried mostly goods and mail -- not passengers. In 1840, the ship Britannia made history when it introduced an onboard cow for fresh milk. This event signaled the shipping industry's new interest in passenger comfort.
Much later, the cruise industry struggled to stay afloat once air travel across the Atlantic became common. But by the 1960s, it bounced back with Caribbean vacation cruises still popular today.