The physics of the operation of the pop pop boat is very similar to that of the "Feynman sprinkler," a submerged sprinkler which is seen to turn weakly or not at all as water is sucked in through it.
Richard Feynman | Wheeler–Feynman absorber theory | Tuva or Bust! Richard Feynman's Last Journey | Surely You're Joking, Mr. Feynman! | Fire sprinkler system | Feynman sprinkler |