Kevin,
Go in the water and swim. Let him see you play with other dogs while you are 12-15 from shore. Then go to shore and pet him. After, walk back into the water and call his name. Tell him to come when you are knee deep. If he won't, get him by the collar. Stand in knee deep water with him. Do this while petting him and talking to him calmly. After a minute or 2, call his name as you go deeper. Show him it is fun in the water, and you enjoy his company while in the water. A tennis ball is also a good tool to play with while near water. Do this a couple times a week, and he will learn to glide with his back riding out of the water. Once he gets the hang of it, he'll love to get in.
