The second clause of your sentence contains the verb is, so it requires a noun clause as a subject. A simpler example would be
riding is fun
There are two choices of noun form for a verb- a gerund or a to-infinitive. In some special cases, you should use a bare infinitive, but this isn't one of them.
This article explains how you should choose between gerund or to-infinitive. In this case, it revolves around whether you are talking about a real or a hypothetical situation. Unfortunately, the tenses in your sentence are a bit mixed up, so it's difficult to tell whether it's real or hypothetical. Let's make two grammatically correct versions, one for gerund and another for to-infinitive:
After you crossed the whole camp on foot, asking for a glass of water was not a surprise. - real, past
If you were to cross the whole camp on foot, to ask for a glass of water would not be a surprise. - hypothetical
Adding an adverb does not change at all the type of verb to use:
After you crossed the whole camp on foot, hurriedly asking for a glass of water was not a surprise. - real, past