Megan weighed in at 110 lbs and was scared to death of water, I took her to the Mississippi river and got her to start biting at the barge foam within ten minutes she was romping and playing in the water.
Next dog, Dusty same problem, we went to a small pond, got on a boat and rowed about 10 feet out, called the dog, she whined at the shore for 5 minutes then finally jumped in and swam to the boat, no more problem.
I reward with only praise, never food or treats, or they will expect it every time.