Remarkable Special Effect
Surprised that no one has mentioned the slow motion umbrella shot where the classmates are throwing him up and down on the blanket.
It may seem passé today but that was an extraordinary effect to accomplish in 1920, going from real speed to slow motion and back. Not only was it funny but mind boggling as to how they did it back then. Optical printers were still in their infancy. There is no change in exposure and it is smooth as silk.
Yet more proof that Keaton was not only a physical comic genius, but a pioneer in Film Technique equal to Griffith & Eisenstein.
PS - What was with the guys getting up in the boat room and their shorts all covered in black?