A tall ship and a water-slide

The photos in this stash are a complete mystery to me. I only have suspicions about the when and where. Taking a guess, I'd say this one was taken, once again near Rochester, New York, likely on the shore of Lake Ontario, maybe sometime from the late 1910s to sometime in the 1920s. I have no idea what that large structure is off to the left of centre. For a minute I thought it might be the 'water-slide' like structure in the photo below, but on closer inspection one can see that that they aren't the same thing. The lower photo came from a different album, and the original is only around 5 cm by 2 cm in size!