We've been going swimming weekly recently, after a long break.
DS just asked me to go swimming randomly one day so I said yes
He's now tall enough to get his toes to the bottom of the training pool, so I think that has helped a lot
The other thing that is working is armbands! I can let go of him and get him to drift towards the pool edge, or hold his hands and pull him along, and his head stays out of the water
We always take a bath toy (a squirty whale) which he can throw and chase or kick.
He will now confidently go down the small slide by himself, I catch him at the bottom, and will sit on the side and throw himself forward into the pool while I hold his hands. We play 'whirlpools' going around in circles holding hands.
I do lots of encouraging 'kicky feet and splashy hands' to get him to start moving in the water, and move his arms for him in a sort of doggy paddle. Sometime I can move his legs but he tends to twist around and get a mouthful of water
He will also let me swim on my back (I just use my legs) while I tow him along, which is great as I'm getting some fitness out of it finally
It's also good for him to see Mama swimming as then hopefully he knows why I'm asking him to do kicky feet
The main thing to encourge is confidence in the water, allowing them to enjoy the sensation of floating and moving around. Once he's older I'll send him to swimming classes and they can teach him the proper swimming strokes. I could do that myself but he'd play up for me whereas he would obey a teacher
That's been our recent experience, so hopefully some of this is helpful!
Enjoy your swimming