Chris Armstrong’s photorealist ocean painting "Shallows" (Link)
The Daughter of King Land-Under-Waves Legend from the Scottish Highlands is recorded in several versions.
One version was recorded by John Francis Campbell in Popular Tales of the West Highlands in 1860-62. The wiki page describing how Campbell came to record this legend is here. The text is widely available and an easy web source is here.
An alternate version was recorded by Donald Alexander MacKenzie, a highlander himself, in his 1917 Wonder tales from Scottish Myth and Legend. Also widely available, it can be read on the web here.
The two tales are obviously related. Both tell the story of a princess visiting from a "Land-Under-Waves" which takes variously three or seven years to travel to. Both stories reference a "Plain of Wonder".