In this context, a chart is a map. To be in unchartered waters thus is the same as flying blind, groping about in the dark. One is finding one's way as one goes without any little idea what lies ahead nor how to get there.

"Uncharted waters" means something that has no precedence...something that is unfamiliar to you because you've never done it before or because you've never been in that situation before. Example: For first-time parents, caring for a baby with a common cold is navigating uncharted waters: when to call the doctor, how much medicine to give, what food to give to boost immunity and expedite recovery.

This is one of those phrases you will never say in your daily conversation with people. But I will tell you two phrases people say instead of that one ... I'm in a boat without a paddle .. (which means I have no oar (tool) to steer the boat to where I want to go.) And if you really want to sound like an English speaker, you say: I'm up shit's creek ... (Which means I'm in a river that smells of 大條) Another way of saying I'm in trouble. But only say that last phrase to really close friends who are your age.

Imagine you are on a boat and you plan your trip very carefully. And sudddenly, a thunderstorm arrives and knocks your boat off course. After the storm, you realize you don't know where you are but you know one thing, you must get back to your destination. This is a literal example of being in uncharter waters. Now imagine, you work for a company and you plan a big presentation for the President of the Beijing office. Before the President arrives, you realize that you are missing some very important material to make your presentation perfect. You don't know what to do do because you have no experience with figuring out this type of problem. This is a figurative example of "being in unchartered waters." So in this situation, you would turn to your co-worker and say, I'm in unchartered waters; which means I have no map to help me take the correct road It implies you have a problem and you have no experience fixing the type of problem you are having.