Suggest Treatment For Dark Circles

I have had dark circles for a very long time now. I didn t drink much water for about 2-3 years but I have been drinking a good amount for about a year. But I just really want them to go away...I look really tired and sad all the time. What can I do to improve them? or to help get rid of them? Also...what causes this dark pigment underneath our eyes. Like what are the dark circles that we see made of?