Vasa Loch is a brackish lagoon in southwestern Shapinsay, Orkney Islands. This water body has been shown on early maps of the island in a very similar shape and size to its current geometry, separated from the North Sea by a narrow strip of raised beach.(Masters, 1840) Vasa Loch is fed by small rivulets and upland springs that rise on the western part of the island's western spur. pH levels of the loch are strongly alkaline, in the range of 10.15.