If it’s high tide, then you can’t see what’s below the surface of the water. But if you see the same spot at low tide, then you’ll know what’s under the water at high tide, and what you might have to deal with, where you might hit the bottom. Relevant to surfing, kayaking, and other things like buying and selling stocks. Try to get a look at the bottom so you’ll know what to do when you’re near there.