Adventures of the Sea Hound was a popular radio show that ran on the Blue Network from 1942 to 1945, Mutual from 1946-47, and ABC in 1948. Between 1942 and 1945, it was produced on behalf of Nelson A. Rockefeller's Office of Inter-American Affairs (1940-46) and was part of a national program to strengthen inter-American relations.
Broadcast five times a week, the show featured Captain Silver and his sidekick Jerry hunting Nazi spies throughout the hemisphere. Every episode took place in a different Latin American country. Listeners were encouraged to write to NBC to request Captain Silver's Sea Chart - a colorful map of the Americas that informed on the most important products and carried on its border pictures of outstanding heroes and flags of all the Latin America republics. Some 200,000 of such maps were sent out.
The show spawned a short lived comic book and the 1947 Columbia serial, The Sea Hound, starring Buster Crabbe. (source: wikipedia)