The fourth USS Shark (SP-534) was a United States Navy patrol vessel in commission from 1917 to 1919.

Shark was built as the civilian motorboat Ildico IV[2] in 1909 at South Yarmouth, Massachusetts.

The U.S. Navy purchased Shark from her owner, Louis Herzog of New York City, on 17 May 1917 for World War I service as a patrol vessel.

Assigned to section patrol duty in the 1st Naval District in northern New England, Shark conducted harbor patrols there for the rest of World War I and for a few months after the end of the war.

Shark was stricken from the Navy List on 16 September 1919 and sold to Morgan Barnes on 20 October 1919.