Eastwater Cavern is a cave near Priddy in the limestone of the Mendip Hills, in Somerset, England. It is also known as Eastwater Swallet. It was first excavated in April 1902 by a team led by Herbert E. Balch composed of paid labourers and volunteers from the Wells Natural History Society. Progress was initially slow, but by February 1903 Balch and Willcox had discovered substantial passage, following the streamway down to the bottom of the cave.