Each individual masturbates differently. Some just use their fingers either inside the vaginal area or on the outside. Rubbing is also common practice. The means by which you masturbate are completely of your own personal preference and can be done while fantasizing, dreaming or just relaxing. So, your use of water, a towel and your fingers is perfectly normal.
A lot of people use water to help them masturbate. One thing to avoid is sending strong streams of water directly into your vagina, as that can be potentially dangerous because of the force of the water flow. Also, make sure that you test the warmth of the water before spray towards your vaginal area, as you wouldn't want to get scalded in that area. It seems like the water that came out of your vagina was from the shower spray you'd done earlier.
Masturbation does not cause any sort of health problems. The only thing you should be careful of is making sure any objects that you insert into your vagina are clean and sanitary- otherwise, using them over time might lead to an infection. So if you decide to continue using a bath towel to masturbate, make sure it's not dirty.
Even though most teenagers masturbate and it is a completely normal and acceptable practice, masturbating excessively can sometimes be considered a symptom of a compulsive behavior. However, there are no criteria to determine how many times a day is excessive and what you're doing right now is obviously not too much. A good general guideline to follow is, if masturbating doesn't get in the way of normal activities and you are not sore afterwards, then you're probably just fine. So, you can feel free to keep experimenting with pleasuring your own body as you see fit.
Other teenagers have had questions similar to yours. For more information, you can check out Love to Masturbate and Teddy Bear to Masturbate.