For Bava, I had to get in the 1st time and lure him in w/ treats and give him treats when he actually swam, but that was just the 1st time., he was ok any other time after that. It did take a couple of times training to get a good retrieve of the bumper from him. Now he lives to save the bumper. Food worked great for him. For Sophie... OMG! She is insane, She just jumped straight out 5' .. Splash and took off swimming away from the bank, and swam for a long time. I don't know if that was her first time or not, since we got her at 6 months, but she definetly has no fear of water. Both of ours were introduced in a pond where there are really no people, or distractions, or waves, I am not sure if that makes a difference or not.
I have to wonder if the waves are scary to them when they're just learning.