Then ask, including lakes, ponds, rivers, and streams how much of the world is water. Make sure the students understand the difference between ocean surface and the total water surface of the planet. PLAY the tape. Water has weight. The more water that is above you the more it weighs and the higher the pressure.
Ocean water absorbs light.
The deeper you go the darker it gets. As a hands on experiment with water pressure, the students will do the experiment with the child on Bill Nye Science Guy. Students are given a preview of the experiment and how to put it together, but are allowed to draw their own conclusions about the outcome. Divide the class into groups of four to five students. Have the pop bottles ready, tops and bottoms cut off two and just the top cut off of one, for each group.