What Breed Is My Dog?

My German Shepherd cross came to me at 5 months old. She was bought at a horse sale from a traveller in exchange for horse feed. She's a one person dog. She is very devoted, loyal, and protective. When out on walks she loves to go in water. She has a sable coat which is a double coat with a soft fluffy undercoat which moults all year round! I have no information on what she is crossed with. What do you think?