The propellor off another guy's boat and the cotter pin or whatever it was that held a cap that apparently held the propellor in place. We found the propellor (good old gravity - it was right where we expected), but never did find the little pin and other pieces he described that were supposed to secure it. Of course, he knew exactly what they looked like because he had just been fiddling with them before we took off on this little adventure.
We were in the middle of nowhere in Brasil, south of Rio, among a bunch of little "islands" that amounted to not much more than a series of sandbars. This happened in the morning. We spent the whole day with most of us looking for the missing pieces, taking stock of our very meager supplies, and getting ready to spend the night when he succeeded in jury-rigging some contraption that held the propellor well enough that we decided to venture very slowly back out into open water where we found another boat that towed us home.