“What is the best medicine for watery eyes?”

There are different reasons for this problem. Most likely it is dry eye and you need artificial tears. It is also possible to have allergy or some chronic inflamation

Depends on the diagnosis. A complete ophthalmologic exam should be performed.

Watery eyes is usually reflex tearing from dryness. Try artificial tears and hot compresses to the eyes.

There are many causes of watery eyes. A first line harmless intervention is over the counter moisture supplements such as Refresh Tears, Systane products, or equivalents. If these fail to relieve your symptoms than consult with an ophthalmology to diagnose the underlying problem and therefore the correct treatment.

Wouldn’t you rather find out WHY you are 25 and have water eyes? See an ophthalmologist.

The best answer is an accurate diagnosis. Then treat accordingly. Starting with a good history including medications such as anti histamines, as well as environmental factors including sick building syndrome. A good slit lamp exam with Lissamine dye and evaluation of the meibomian glands. Followed by ancillary testing such as osmolarity evaluations and MMP-3 evaluation of inflammation will most likely allow formulation of the diagnosis and treatment. In the meantime, one could use a preservative-free artificial tear substitute.

Artificial tears, refresh or systane, four times a day (breakfast, lunch, dinner, bedtime).

Depending on the cause, lubrication will help

One's eyes can water for many different reasons. Do you wear contacts? Do you have allergies? Are you noticing this happening when looking at a computer screen or reading for a significant amount of time? It really depends on why your eyes are watering which can be diagnosed by a physician; however, for many people the likely cause is from surface dryness. I know this can sound counterintuitive, but if the surface of your eyes are dry, your body responds by trying to lubricate said surface resulting in significant amounts of tears. The best way to ameliorate this is by using artificial tears regularly. I liken this to moisturizing one's hands so they don't become dry.
When purchasing over the counter artificial tears, make sure you do not buy things for redness or allergies; these have medicines in them that you do not need. There are many good brands out there so do not be overwhelmed by how many choices you have.
Consider keeping the bottle of tears in the refrigerator as the cool temperature is soothing. You can use them as needed when your eyes are watering/burning. You can also consider using them four times a day regardless of symptoms to prevent watering. Again, think of this like using moisturizing lotion to prevent skin dryness before it happens.