I took dd to Aquatot type class when 5 months old, and she didn't exactly hate it - but was noticeably underwhelmed. It wasn't fun for either of us, tbh - and I think the water was far too cold, which didnt' help.
After that, I backed off and just tried swimming with me/dh for fun occasionally (in warmer pools) and she was happier, but still not overly keen - and a bit clingy.
Then suddenly, at about 2.5, she loved it - I think she had become confident physically in other ways, running, climbing etc, and it helped her in the water. From clinging to me, she went to splashing around on her own with armbands on and wanting to be shown how to swim without them - and the change came from inside her, not from anything I did. Before that, she wasn't ready - and no amount of classes, pushing, begging, or role-modelling was going to help.
I honestly wouldn't worry too much at this age: fun with you/dh, enjoying the bath, all that is GOOD. Swimming classes if he enjoys them, fine - but if not, I'd vote for stopping, personally.