I have a tiny clear bump that looks like a water blister. it's on the water line of my eye and frequently comes and goes with swelling.

Cyst or other: Difficult to say what it is. Cysts of the eyelid usually do not come and go. Recommend a check with your eye doctor in the next few days. Take a pix if you can for your md.

Cyst: It sounds like you most likely have a cyst. It is very typical of cysts to change in size. If they bother you a lot, they can be either "popped" or completely removed with a simple, short surgical procedure. Some people can have cysts on the eye itself, or on the eyelid. If it is bothering you, you can have an ophthalmologist evaluate it.

Could be chemosis..: If it's on the white of your eye, it's likely chemosis of the conjunctiva, which is when clear fluid builds up blister-like under the conjunctiva in response to allergy. It goes away when the underlying eye allergy is fully treated. If it's on the eyelid, it may be blepharitis or sty. In either case, you may need some more prescription drops from the ophthalmologist.