USS Thetis (SP-391)

The USS Thetis (SP-391) was a United States Navy patrol boat in commission from 1917 to 1919. Thetis was originally a private motor yacht built in 1916 by the Matthews Boat Company of Port Clinton, Ohio. The U.S. Navy acquired her under a free lease from her owner, L. A. Gillett of Cleveland, Ohio, on July 31, 1917, for use as a section patrol craft during World War I. She was commissioned as USS Thetis (SP-391) on August 24, 1917.

Assigned to the 9th Naval District, Thetis performed patrol duties on the Great Lakes for the duration of the war. Her specific operational details are limited, but her general role would have involved enforcing neutrality laws, conducting anti-submarine patrols (although a remote threat in the Great Lakes), and potentially aiding in training activities.

Following the end of World War I, Thetis was decommissioned on December 10, 1918, and returned to her owner. Her subsequent civilian history is not well documented.