What you needA variety of objects that sink or float such as Containers, Rocks, Bath toys and other items.
Plastic tubs or buckets to place the water in.
Water provides a great learning activity as when they play with water they explore what happens when they try different things with it like pouring and measuring water, or what the water does in a container, or how many spoonfuls it takes to fill up a measuring cup, and so on.
Taking your large tubs and filling them with water. Sit your group around the water and place all the water items in a pile.
Select a few items out and show them the difference between sink and float. Have each group member select an item from the pile, you can ask them to choose a certain colored item if you wish to extend the learning capabilities of this activity.
Before the item is placed in the water ask them whether or not they think it will float or sink. Large sitting and standing movements could have your group imitating the sinking and floating concept for a more physical activity.