How can i stop my dog from wanting to go in water when off lead on walks?

I think to keep him leashed. I'm very glad to hear that your dog has such exceptional recall that you can call it back from a major distraction. If he gets a relapse in his training, well, the results shan't be pretty. Worse comes to worse, harness him and put him on one of those flexi leads, you know, the ones that roll out really far? Worse comes to worse, when he's near a stream, he can still be in control, but still be contained.