It is normal to get watery eyes after a whole day working at a computer. Some people also called it computer vision syndrome. Also, you can say the symptom as eye strain. Your get watery eyes because your eyes are tired result from seeing computer. Besides, for people work with computer, they may also suffered from sore eyes sensitivity to light , blurred and double vision as well as pain in the neck and shoulders etc. If you have those symptoms, you must take care. Take a regularly break when you work. Also, you shall do exercise daily to help you build healthy body so as to fight against computer vision syndrome such as eye strain.
In common, people with eye strain can get watery and red eyes. Besides, they may also suffered from pain in the eyes, sensitivity to light, blurred vision or twitched eyelids etc. If you have this experience, you are suffered from eye strain. Don't worry, eye strain is not an eye diseases or eye problems. It is a symptom of tired eyes. Taking a good rest, your eyes will recover. To help you prevent eye strain the next time, you are suggested to take a break every hour when you work with computer. Hope this can help you.