I have had four Newfs, and only one of them swam like a fish when they first went into water.
I have an old Newf, Molly, who was 10 this summer. She only decided this year that she liked water and now she will swim whenever she can, and she is a bugger to get out of water!
My second Newf, Bronte, was the one who always swam like a fish. Sadly she is no longer with us.
Then I have Honey, she can swim, she has been out to "rescue" my daughter. But she isn't that bothered about water... Other than playing in it!
And then their is Kitten, the only male and a complete wuss. We have managed to get him to swim a couple of times, but he starts to panic once he realises his feet are off the floor. The one time he did swim it was just to get to his sister Honey, who was on the bank of the lake, and Kitten jumped out of the boat and swam to her... We were actually hoping that she would swim out to the boat!
I just leave them to it, if they want to swim they can, if they don't want to then it is up to them!