build a boat out of natural materials you find outside. see if it floats (10 points): my plan was to make a little raft with a lashed base and a woven mat, but the materials turned out to be harder to work on a short time budget. i got a thing that held together and floated, at least.
build a kite and fly it (10): i still have my little kite downstairs. you know, just in case.