The Bay of Skaill on Mainland Orkney is famous because it is the location of the wonderful remains of the Skara Brae village. The bay is pretty spectacular too. At 1 km wide and 1km deep it is one of the largest on the island. It is predominantly bed-rock sub-tidally, with a lens of sand-sized sediment in the intertidal, and a cobble barrier protecting the ‘machair’ hinterland (Fairley, Karunarathna, and Chatzirodou 2017). The rocks of Bay of Skaill represent sediments of the Old Red Sandstone which were deposited in the Devonian geological time period, about 380 million years ago. They are composed of the Upper and Lower Stromness Flagstone with the intervening Sandwick Fish Bed (part of the Caithness Flagstone group) and several intrusive igneous dikes made of camptonite.