Apples are 25% air, which is why they float perfectly in water.

Whether something floats or sinks depends on its density. Water has a density of 1.0 gram per cubic centimeter. Because an apple is filled with so much air, its density is only about 0.8 grams per cubic centimeter. Since the apple is lighter than the water it pushes aside, it stays afloat.These air pockets are found in the apple's parenchyma tissue. They aren't in one big bubble like a balloon. Instead, they are tiny gaps between the cells. These gaps are very important because they help the fruit 'breathe' by letting oxygen and carbon dioxide move in and out.Other fruits don't have this same design. For example, pears and grapes only have about 5% air inside them. This makes them much denser than water, so they sink straight to the bottom of a bowl. Scientists in the 1950s even found that different types of apples have different amounts of air. A McIntosh apple might float a little higher than a Granny Smith!This simple bit of science is the reason people can play the game of bobbing for apples. If apples were solid all the way through, they would sit at the bottom of the barrel and the game would be impossible to play.