Answer the question in the negative.

Est-ce que tu fais de la voile?

I know that it is asking me something about sailing but I'm not sure exactly what it's asking.

Tu: personal pronoun, second person singular.

Fais - second person singular for "do".

"Est-ce que" is a standard phrase to introduce a question without inversion of subject and verb. Similar to

"Is it that..."

Non, je ne fais pas de la voile.

Non, je ne fais pas de la voile.