I have duck retrievers, and I once threw a pigeon for my retrieving-mad Newf, Rain. He ran out to get it... and looked up with THE most horrified look I've ever seen. "But... but... it's DEAD!"
Hee. If you worked with them to get them willingly retrieving both dead and crippled birds, you could use them. However, while they would probably be better suited for cold water than the retrievers, they wouldn't have the speed or the endurance, and it would be AWFUL to try to haul them out of the water between retrieves if you were hunting from a boat.
(You don't want to leave them in the water. Hypothermia hits fast, and it's a very ugly death.)
I would love to be able to train my Newf for hunt tests. The organizations that put on hunt tests, however, discriminate against non-retriever breeds. Sigh.