This reminded me that when I was young, I had a toy submarine. You’d put a tablet - like an Alka Selzer - into it and it would sink to the bottom of the bath. As the tablet dissolved, the thing was supposed to rise to the surface but mine leaked so it was destined never to get to periscope depth! The toys here all start off similarly benign enough, but gradually they turn into playthings altogethever mais...