The mystery of Buffalo Lake

Here's a mystery of old Alberta:

Buffalo Lake, in central Alberta, was called Buffalo Lake because it was shaped like a buffalo with Tail Creek, the outlet of the lake to the Red Deer river, as the tail.

But how did people know how it was shaped unless they could see it from above?

Source:

"The Edmonton Hunt" by F.C. Jamieson, Jan. 23, 1951 (in PAA "Buffalo Hunts" info file)