It is made from freshwater fish, unlike the better-known Bouillabaisse, which is made from saltwater seafood.
The fish used are eel, salmon, and carp. The broth is based on fish stock, and either red or white wine.
The fish is skinned and filleted. The disposable parts of the fish are first used to make the stock, then the rest of the fish is used in the soup after the broth is all done and strained.
There are several variations. Matelote Normande, for instance, uses hard cider as is typical of Normandy instead of wine.
“Matelot” in French means “sailor.”