Spartan Gold. FARGO Adventures #1, Paperback/Grant Blackwood

Adventurers and treasure hunters Sam and Remi Fargo are on a wild-goose chase. Up to their waists in the Great Pocomoke Swamp in Maryland, they're hunting for lost gold. What they find instead is a small Second World War German U-boat. Inside the submarine they find a body - and a puzzling, incredibly rare bottle of wine.