There's much to see under the sea, but you need to remember that light behaves differently in water than in air. The objects appear closer to you than they exactly are. You might find yourself reaching out to touch something and completely missing it.
Objects under water will appear larger than they would on the surface, too. Be careful not to tell any stories about the big fish that got away. That fish might not be so big after all! It's just because sometimes things can seem to be as much as about 33 percent bigger in water!
What's more, in deeper water, colors just don't seem as bright. In fact, it looks as if some colors are missing. Remember the color of an object results from the wavelengths (波长) of light that are reflected (反射) from its surface. And light is taken in as it moves down through the water.
Swimmers wear wet suits to keep warm underwater. Let's take a bright red, yellow, and blue wet suit as an example. These colors are hard to miss on the surface of water. Watch carefully the changes in color as you descend in the water. The red part now looks almost black because the red light wavelengths, the longest among these three colors, are missing. As you go down deeper, the same thing will happen to the yellow part and in the end to the blue part. Even at a place of about 6 to 9 meters underwater, you will look terrible, like a ghost! And you have to wait for your return to the surface to enjoy the bright colors again!
