Bumpy-bumpy

Anna, do bumpy bumpy. 

Y orders her brother every few minutes in the swimming pool. Resigned, he stops whatever he is doing (which is trying to float on his back, and practising his freestlyle strokes), takes her in his arms, and bounces and whirls her all over the water while his sister shrieks in pure delight.

Duty calls. Even in the swimming pool!