This is the most dangerous whirlpool in the Pentland Firth, just to the north of Stroma, it is caused by the meeting of four or five contrary tides. According to Icelandic legend, the Swilkie is the place where the salt which maintains the saltiness of the oceans is ground in a giant quern, stolen from King Frodi by a sea-king named Mysing. When Mysing's longship sank off Stroma under the weight of it, he still continued to grind away with it 15 fathoms down.
