A question about optics...

In college, I noticed my eye sight beginning to deteriorate. I was once able to sit in the back of the lecture hall and see the board clearly, and then sat in the front of the same room and could barely make out a word on the board.

In the transition period between having 20/20 vision and absolutely needing glasses to read something on the board, I made an interesting discovery.

I found many lectures quite boring, and often did not get enough sleep the night before, and so I did a lot of yawning in class. What I noticed was that when I yawned, my eyes would naturally tear, and when the tears would well up in my eyes, my vision would be miraculously restored seemingly to 20/20 as long as I kept the water in my eyes.

I also know that when you put a fish in a tank and look at it from above, it looks much smaller than if you were to look at it from the side of the tank. Water obviously distorts vision (how?), and yet it amazed me that simple tears would distort vision perfectly enough to compensate for my failing eyesight.

How does this work?

And then, how does this work?