Well, if he retrieves in water, you're halfway there. I have seen descriptions of clicker training for retrieves, and our class does a type of that kind of training without the clicker (say special word and treat instead of click and treat) and to tell you the truth, it would bore me to tears! These people have spent months just getting their dog to nose the dumbell. I think there is one called "21 incredibly boring steps to get your dog to retrieve (or something like that - just kidding!) I have seen the steps, but a quick google search didn't turn it up.
I'm assuming this is for obedience, but you can force fetch her just like you would for hunting retrieving. I really like the smartworks series by Even Grahm. You would only need the first book "Smart Fetch".
I'd pm FallRiver because I'm sure she has the clicker info.
The key to teaching a reliable retrieve is to break it down into the smallest steps and go V-E-R-Y S-L-O-W-L-Y. The problem most people have is they go from putting the DB in the mouth one day to asking the dog to retrieve the next day. There are tons of steps in between and it takes months to get a reliable retrieve.
That's right - there are many steps! My dog basically had a very nice retrieve and would deliver it to the front of me and drop it practially from pupphood on. But when we learned how to do it "for real", we started with "take it", getting them to reach out and take the dumbell - then "hold it" (don't drop it until I say so), then you go from there - not actually throwing it for quite a while.This is the area where the infamous "ear pinch" raises it's head also - so be prepared for that decisioin.