no matter how much water i drink,my eyes wont lighten up. I drink at least 1gal of water a day and it isnt helping.

im in high school and people constantly ask me about my eyes. i doesnt bother me im just tired of the same question. but i do notice when i first wake up from sleep, they are more clearer than before. but as the day goes on they get right back dark. is there any medicine that can help with my eyes?