Good to see this up here! My version is very close to Louise's:

Oh Jemima look at your Uncle Jim!
He's in the duck pond learning how to swim.
First he does the breast stroke, then he does the side,
Now he's under water, swimming against the tide!

My Dad used to sing this. My parents were Scottish, but we lived in Lancashire for a few years (guessing that's where he picked it up) before moving over the Pennines to Yorkshire. I had an uncle called Uncle Jim - maybe that's why this little ditty stuck in my head. I sang this little song to my old friend Stanley Robertson a few years ago at Whitby Folk Week.