Calvin personalified the tadpole stage addressed by the lyrics of this children's song. It continues,
"Hey polly wiggle and hey polly wog,
One of these days you'll be a frog,
You'll kick your legs and swim around,
With never a splash and never a sound.
(Make rhythmic croaking sounds)

He got to enjoy zooming about a large pool balanced in various athletic postures on dad. And with me, he got to try out proto-swimming moves akin to wiggle, wriggle and kick. Calvin became quite fascinated with the idea of blowing bubbles in the water and was quite cavalier about getting his face wet.

Undoubtedly, his favourite pool time was in the baby pool... But you'll have to wait for the next installment to hear more about that.