In water, the direction along the stream is called downstream. And, the countercurrent direction is called upstream. The water that remains until it doesn't flow is called still water. The speed of the boat in calm waters will vary from that of the stream water.
But based on the speed in the stream, you can calculate the speed of the boat in calm waters. Here is the calm water boat speed calculator that gives you calm water speed and stream speed based on the speed of the boat upstream and downstream. This tool obtains the result based on the commonly used calm water velocity formula.