Have preschoolers test an object's buoyancy by dropping it into the water table. Objects that float have positive buoyancy, while objects that sink have negative buoyancy.
Create current in the water table by adding water with a hose or creating a whirlpool by stirring the water with a spoon. Watch the movement of toys as they are caught in the current.
Add sand to the water table to demonstrate erosion. Hide dinosaur bones or other toys in the sand. Create current and watch as the sand is eroded to reveal the toys beneath.
When dry ice comes in contact with water, it produces a boiling effect and causes a fog that fascinates preschoolers.
Every water table can benefit from having basic toys available. Include measuring cups, funnels, whisks, eyedroppers, toy boats and other creations. Line the bottom of the table with aluminum foil for a shimmering effect and add rocks, beads and other treasures to the bottom.