The surf mill

Few people have heard the sounds of the surf mill practically from within the sea, as described by Henwood after his visit it a British mine extendinng out under the ocean:

"'When standing beneath the base of the cliff, and in that part of the mine where but nine feet of rock stood between us and the ocean, the heavy roll of the larger boulders, the ceaseless grinding of the pebbles, the fierce thundering of the billows, with the cracking and boiling as they rebounded, placed in tempest in its most appalling form too vividly before me ever to be forgotten.'"

-- "Transactions", Geological Society of Cornwall, vol. 5, 1843,
quoted in Rachel Carson's The Sea Around Us