Think about it. When you draw earth on a piece of paper, what is it? FLAT.
When you have impaired vision and don't use your glasses, what's the horizon? FLAT
If on the off chance that you have good vision, look at the horizon. Oh nevermind there's trees blocking your view but guess what it looks FLAT
Think about your shoes. If the earth was round, your shoes would need to be curved too, or walking would feel weird. What does that mean. The earth is FLAT
Why are there waves you say? Because of the weight of humans are disproportional across the world, lots of people moving keeps tilting the earth so it keeps causing waves. Screw it. The moon doesn't do nothin, because the earth is FLAT