It is normal for the eyes to water while yawning. Actually, our tears are excreted every second. Just because of the canalis nasolacrimalis, the tears are not shown in the eyes. However, when we jawn, the pressure of the canalis nasolacrimalis becomes bigger and the tears will show in the eyes. However, if you often have this situation, you'd better have the check in the hospital to see whether the nerves in the eyes are normal.
Yes, it's very normal for your eyes to water while yawning. This happens to everyone. So you should not too worry about it. When you yawn, the muscles in your head push against your tear. Then it forces the release of some of your tears. That's why you have some water in your eyes and make other people think you are crying. But, if your eyes are sensitive, it will make your eyes more watery than others. In this situation, you must go and see a doctor first, and have a test. Then decide the treatment.
This is a common phenomenon. While yawning, your mouth open in a large feet may and let the air exhale from the body for exhaling carbon dioxide and inhaling oxygen. With the action of yawning, surge of gas exhaled from the mouth. Cheek, tongue and throat's muscles tensely contract, at the same time the oral and nasal's pressure increases, which will lead to a moment to stop the nasolacrimal duct excreting the tears. The tears can not stream down, and the area of the tears in the eyes will be more and more, and finally roll down in the face.