Uncharted waters is a common phrase used to describe unfamiliar territory. Don't make the mistake of writing unchartered waters instead.
Harbour picture from Shutterstock
This error is understandable: in spoken English, the two phrases sound essentially identical, unless you go out of your way to enunciate carefully. However, unchartered waters makes no sense: it means, roughly, "waters that haven't been hired". What you want to say is "waters that haven't been mapped".
If you can't reliably distinguish between the two, choose a different phrase like "unknown areas" instead. Accuracy matters.
Lifehacker's Mind Your Language column offers bossy advice on improving your writing.