He's becoming a teenager, and figuring out his role in the world. If you have him on a leash, as soon as he starts barking, give a quick tug on the leash and get his attention. Make him sit, go through a series of commands - whatever, just to break his attention away from barking and toward you. Redoing obedience training might help. He's figuring out his role in the pack, and you have to remain the "big dog" through these challenges, you'll both be happier this way!

If he doesn't like water, a spray can of water will be more effective than rattling the can.