The yellow line represents the tape measure we used to measure the depth of the pool. The beaker is showing the volume of the air bubble at different depths. As you can see the volume of the air bubble decreases in size as the depth increases.
This diagram shows our dry experiment. The circle on the bottle left of the pump represents the pressure gauge. You can see as the pressure increases the volume of the air bubble decreases. The beaker is inside of a 2- liter soda bottle. The brown object in the bottom of the soda bottle is a weight we used to keep the beaker down.