Three yachts associated with Dark Island were Artemis, Sioux, and Dark Island. Artemis, owned from 1898 to 1909, was a twin screw steam yacht designed by Mr. Gustav Hillmann and built by C&R Poillon of South Brooklyn, New York, in 1897, with a length overall of 82 feet 10 inches, a beam of 13 feet 10 inches, a depth of 5 feet 6 inches, a draft of 4 feet, and steam power. Sioux, owned from 1910 to 1919 and later belonging to Marjorie Bourne, was designed by Mr. Nathaniel G. Herreshoff and built by the Herreshoff Manufacturing Company, with a length overall of 111 feet, a beam of 11 feet 6 inches, a depth of 5 feet 10 inches, a draft of 3 feet 11 inches, and steam power. Dark Island, owned from 1912 to 1919 by Marjorie and then by Alexander Thayer until 1938, was designed by Charles L. Seabury and built by the Gas Engine and Power Company and Charles L. Seabury and Company in 1912, with a length overall of 60 feet, a beam of 10 feet 6 inches, a depth of 4 feet 9 inches, a draft of 3 feet 1 inch, and gasoline power.