Whales and Whaling
The crows nest on old time sailing ships was a barrel shaped unit attached high up on the main mast where a sailor would climb when on watch for ice or whales. This was the highest point on the ship and of course afforded the best view so was the best position to spot whales from.
No your eyes don't deceive you, this particular crow's nest is not up a mast, but on the deck with a salty old sea dog posing with his telescope for the camera. The reason for this presumably is that when the crow's nest/salty old sea dog/telescope are in place atop a mast it would be all but impossible to achieve this photograph with the relatively primitive equipment available.
Picture used courtesy NOAA