Growling/barking around dogs in water

Question
Hi,
I have a one and a half year old Lab/Shepherd mix. He is neutured and has taken obedience training (clicker, and is just starting agility). We adopted him from a rescue organization, and have had him about five months.
My question is about growling/barking, and how to know when it is just for play.
I take him to a park everyday where he can be off-leash and interact with other dogs. Once in a while he will growl at a dog or two, but will then just end up playing with them. He gets most excited, however, around water, where other dogs are swimming and fetching sticks. At these times, he spends most/all of the time barking and growling at the dog that is in the water...like he doesn't know what to make of it. He really gets in the dog's face, just barking and growling, and does not listen to me when I say "No." Usually, the other dog just ignores him.
I have only taken him to the water a few times, so my guess is that he is afraid of the water somewhat, and shows this by acting out like that. I was wondering what suggestions you might have to help with this. My guess would be to take him to water more often on his own to get him more comfortable..then go with a dog that he knows, to break him in more. I'm thinking that in the meantime, I should keep him on leash if there are other dogs playing in the water, and remove him if he starts barking/growling?
Thanks.  

Answer
Get in the water. He doesn't see you in the water so he feels it is wrong for another critter to be inthe water. Go to a beach where you can walk barefoot in the water and coax, not force your dog to walk in it too. Show him there is nothing to fear. Do it on lead. Then try a ball, stick whatever for your dog to play with in the water.

Lacking a beach you can use one of those plastic kiddie pools.

Regards,
Henry Ruhwiedel
Westwind Kennels LLC