Sea bathing is swimming in the sea or in sea water and a sea bath is a protective enclosure for sea bathing. Unlike bathing in a swimming pool, which is generally done for pleasure or exercise purposes, sea bathing was once thought to have curative or therapeutic value. It arose from the medieval practice of visiting spas for the beneficial effects of the waters. The practice of sea bathing dates back to the 17th century but became popular in the late 18th century. The development of the first swimsuits dates from the period as does the development of the bathing machine.

The practice of sea-bathing developed starting in the mid-1800s into the modern cultural phenomenon of beachgoing. In the 19th century, the introduction of railways led to the further development of seaside resorts and bathing boxes. The death of large numbers of people while swimming in the open sea led to the introduction of surf lifesaving in Australia and lifeguards throughout the world in the early 20th century. With the extension of scheduled air transport since the latter half of the 20th century, the development of seaside resort areas such as Ibiza in Spain, the Queensland Gold Coast in Australia and the Miami metropolitan area in the U.S. attracted millions of visitors annually.