[T]he purpose of the bathing machine was all about those crazy rules of bathing etiquette that they upheld in the 18th and 19th century, which kept women and their beach bodies out of sight.
The wooden carts with two doors on either sides allowed bathers to change out of their clothes and into their bathing suits without having to be seen by the opposite sex.
The four-wheeled box would be rolled out to sea, usually by horse or sometimes human power and hauled back in when the beachgoer signalled to the driver by raising a small flag attached to the roof.
Some machines were equipped with a canvas tent lowered from the seaside door, capable of being lowered to the water, giving the bather greater privacy.
Once deep enough in the surf, our bather would then exit the cart using the door facing away from prying eyes on the beach and proceed to paddle.
Via Messy Nessy Chic for lots more pictures and the full article.