How deep is the water?
I like to use a lifejacket on Jackson; he's a GREAT swimmer but he likes the comfort of the jacket when jumping and it gives him confidence.
My dad has a pool (in-ground in his yard) that he uses all summer and we're doing our first "official" dock diving this weekend.
Jackson showed interest in water from a young age, even before the pool was open. So his very first summer, he was about 7 months, he never jumped in the pool at first. He would only lay on the steps and come swim when I helped him in.
Then, I bought the lifejacket which gave him confidence. I used a blow-up raft and encouraged him to jump onto it, which he started doing, and I'd throw a toy in. He instinctively seemed to know to retrieve it. For two summers, he would jump onto the raft first, THEN jump into the water from the raft. Last summer, he finally began diving off the edges!
I just always made it very fun and encouraged it, I also used food at one point to lure him in, and he realized how much he loved it.