Re: What structure in your eye makes it water.

There is a gland under the upper eyelid, toward the outside edge, called
the LACRIMAL GLAND.  This produces tears which are spread across the 
eye with each blink to keep it moist.  The tears them drain out through
the "tear duct" on the inside corner of the eye, and into the nose.  

An eye that waters too much can either have an overactive lacrimal
gland (which is often the body's way of trying to flush out irritants)
or it can be a blocked tear duct, a rather common problem which often
requires a physician's help.