We are working on this issue as well with our 4 month old. I have watched a lot of videos /read threads on dog reactivity. You can find them easily with the search tool on this forum. The last two weeks, I have taken him to a local park that has a dog park near it, but keep my dog far away enough that he is not reactive (aka below threshold). Petsmart is "above threshold" for your dog (and mine too) right now so you won't be able to train him out of this there. You will have to work up to it.
Start further away from other dogs and work your way closer to them as you see him react less. Don't use the clicker to "get" his attention. You click during the wanted behavior. For me, the wanted behavior is for him to have his eyes on ME. When my dog looks away from the dog (or other distraction) and at me, I click and treat. I am using the command "watch me". Other trainers us "look at that" which trains the dog to see notice the distraction, but return their attention to you (initially for a treat). As we progressed, I would play tug, etc with him. It's all about YOU!
My neighbor that has a very stable 7 year old dog has let me practice with her dog by having her dog out across the sidewalk while I work with my dog on our side of the street. After two weeks of this training, I am proud to say that we took both of our dogs for a walk together tonight and my new pup did great! The reward for making it around the block with manners was a really fun play date when we got back home and I had a tired pup that went right to sleep when we got inside....and I let out a big exhale!
My dog barks at other dogs because he thinks he gets to play with every dog that passes. We begin agility and freestyle training tomorrow and he can't be acting all crazy after the other dogs while he should be training with me so I am hoping he is desensitized enough to stay focused on his training (which he loves!). "Other dogs in the room?? No big deal Mom!" That's what I am hoping he will say tomorrow! ;-)
And my dog loves the water so much but hasn't gotten in the pool yet. He splashes in his water bowl and makes a mess and he loves the man made waterfall at a local park. We live in az though so we are hoping he takes to actual swimming this summer!