Testing the waters means trying something out to see if it's okay or safe before you dive in. Just like when you want to go swimming, you might stick your toe in the water to see how cold it is before jumping in.
When people talk about testing the waters, they're usually talking about trying something new, like starting a business or a project. They might want to see if people will like their idea or if it will work before they invest a lot of time and money into it.
So, testing the waters means taking a little test or trying something out to see if it's worth doing or if you'll be successful at it. It's a way of being cautious and not jumping into something without thinking about it first.