Can I Cover Up A Tattoo With Makeup...?

You could try using waterproof concealer. It would really help even if you're going to wash it with water so if you want, you could just first try it at home and check which brand is really effective. But of course just for you not to worry about the remedy, why not just tell it to your parents? I know they will understand you.. You are their daughter anyway, with or without tattoo... Goodluck! (^_^)

Depending on the colors, it's going to be hard to cover a tattoo with ordinary makeup.  Have you considered that the makeup would wash away in the water?  The best thing to do might be to come clean about it.  Apparently the tattoo can't be seen when you're clothed.  You know your parents better than any one else