I like a girl in the same class as me and when we went on a field trip I accidentally sprayed her with water from the fountain. What should I have told her?

Hmmm....what should you have told her....sorry?

How do you accidentally spray someone from a water fountain? And how does having done this put you into "trouble"?

If it was an accident, you apologize.

You sincerely apologize to her for spraying her with water. Probably too late to make amends, but try hard.

How old are you? If that was an accident! Apologies to her, you said you like her! Hmmmm so that's the trouble! May be you can give some chocolates(real one) or flower with your apologies! Girls like chocolates! That may work! ;)
All the best!