The 1936 Cleveland-Great Lakes Exposition half dollar had dual commemorative objectives: 1) to mark the centennial of Cleveland's incorporation as a city, and 2) to celebrate the city's hosting of the Great Lakes Exposition which was held to commemorate the centennial; the Exposition ran during the summers of 1936 and 1937.
The reverse design is what makes it work for this "Pieces of the Sea" thread. The coin was designed by Brenda Putnam. On its obverse is a left-facing portrait of General Moses Cleaveland (correct spelling). On the coin's reverse is a map of the Great Lakes area with its major cities noted via stars. The largest star seen - with one of the points of the over-sized caliper pointing to it - represents Cleveland. A caliper, as depicted, was used (especially) in early navigation. It is a measuring device with two pointed tips that can be used to accurately mark the distance between two points on a map.
1936 Cleveland Centennial and Exposition Half Dollar
For more about the Cleveland commemorative half dollar and its original holders, check out:
I think the 1928 Sesquicentennial of Hawaii's (European) Discovery half dollar works for the theme.
The coin's obverse presents a left-facing profile of Captain James Cook (w/o his ship) along with a very small compass that is shown pointing north. At the border on the obverse is a series of small curves meant to symbolize waves on the sea.
The reverse design includes a scene depicting King Kamehameha I in the foreground atop a hill and under a coconut tree with the waters of the Pacific Ocean rolling up onto the sands of Waikiki Beach in the background - no ships in sight!
1928 Hawaiian (European) Discovery Sesquicentennial Half Dollar
You can learn more about the Hawaiian commemorative coin by checking out: