What is an object that will sink in a small tub of water and then float after 1 minute?

This is for a science experiement that I am doing in one of my elementary education science classes. I can use any object that will sink and then float. The trick is that the item must be placed in water and not any other substance that could potentially help it float. Any ideas?What is an object that will sink in a small tub of water and then float after 1 minute?
Well, if you can get the water hot enough before dropping it in, how about an egg?What is an object that will sink in a small tub of water and then float after 1 minute?
The bar of soap