Dr. McCredy had this bath cut into the sandstone on the shore at Corrie on the Isle of Arran, Scotland, in 1835 to treat his patients with seawater therapy.

Measuring around 12 feet long, five feet wide, and five feet deep, the Doctor’s Bath could accommodate several patients at any one time. It features a number of channels that allow the basin to fill up with seawater when the tide reached a certain level, before the water actually got as high as the bath itself. 

Thalassotherapy, or seawater therapy, became popular in the 18th and 19th centuries. Swimming or wading in the ocean, seawater pools, and heated saltwater baths were common.