What breed mix is my dog?

Question
Hello,

I have been racking my brain (and that of others as well) trying to figure out what breed mix is my dog!  He is 7 months and 50 pounds.  He was originally from a shelter in South Boston, Virginia, and he was transported to a shelter in Haverhill, Massachusetts (where I got him at age 3 months).  The shelter in VA said he was a chocolate lab/chesapeake bay retriever mix... and the shelter in MA just relayed the same information.  

At age 4 months, I brought him to the vet and he didn't really make a guess, he said he was too young to tell, but that the shelter's assumption was pretty good.  As he's grown, he's developed very long fur on his tail (similar to a golden retriever) and very thick, wavy fur between his shoulder blades and at the base of his tail.  

He is chocolate in color, with tan markings on his paws, stomach, bum, chin, and eybrows (like a roteweiler).  He also has light-tan eyes and a pink nose (like a chesapeake bay or australian shepherd).  

He has a very mature and calm temperament for his young age, has a strong desire to please, LOVES the water, he's very happy and bouncy and loves everyone and everything, he is quite smart and picks up quickly when learning new tricks, he adapts well to different situations, never barks, and is very well mannered.

The guesses (made by myself, family, friends, and strangers) are:

Chocolate Lab
Chesapeake Bay Retriever
Golden Retriever
Flat Coated Retriever
Rotweiler
German Shepherd
Australian Shepherd

Any help, guesses, or suggestions would be GREATLY appreciated!!

-Sarah

Answer
You can get blood work done at a vets and sent away for DNA results I belive. But from the markings you mantion I have seen those in rottys/shepardX's and husky crosses ausse shepard also often have the same over eye markings. The wavy fur can be from the cheseapeake retriever or from a golden retriver/aussie shepard...the long tail hair can be from aussie shepard/golden retreiver/husky/shepard.