"bathing machines"

Bathing machines were like small wooden beach huts with wheels, which enabled them to be wheeled into the sea.  They were designed to preserve the modesty of female bathers (whose costumes were considered revealing at the time) by concealing their entry into the water.

Mermaids at Brighton, by William Heath
Public DomainMermaids at Brighton, by William Heath
1891 photograph of a bathing machine
Public Domain1891 photograph of a bathing machine