Question

on the map, #2 is identifying which body of water?

Explanation:

The map shows North America, and the area labeled #2 (near the Great Lakes region, likely Lake Superior or part of the Great Lakes system, but more precisely, looking at typical North American water body maps, #2 here is likely Lake Superior or the Great Lakes' upper - central part. However, a common identification for this position (near the Canada - US border in the Great Lakes area) is Lake Superior or the Great Lakes. But more accurately, in standard North American water body maps, the body of water at position #2 (between Canada and the US, upper Midwest - Canada border) is Lake Superior (part of the Great Lakes).

Answer:

The body of water identified by #2 is Lake Superior (or part of the Great Lakes system, with Lake Superior being the most probable specific lake at this position).