I would keep with it wrt swimming. My DD hated it for the first few months I took her (albeit it was early at 3mo). Now, she loves it and anything to do with water. We went to the beach today and she spent the whole day on the water!
A paddling pool works wonders here, as does the 6ft trampoline we bought her for her birthday. Honestly, I can't get her off it!
Yk already that we walk miles so I won't suggest that again if he's not up for it, but just walking to see something he's interested in.. For us here, we go and stand on a bridge above the motorway so she can name all the buses, lorries, tractors, caravans etc. We sometimes take toy things like a toy car and she has to turn around, cover her eyes and count and I hide the toy. She'll then spend ages looking for it. We do this in the garden and even on our walks. Forgot to add.. We also swap this around in that she'll hide the toy and I'll have to find it by saying.. Is it by the tree? And she'll answer 'no', is it by the blue flower etc etc. It's a great way of them learning what things are without enforcing it on them. In the garden, she has better hiding places than me! And she'll actually eventually tell me where it is by naming it., ie the ball.. red bin!!!
Hth xx