So, in Half-Life 2 they had this really awesome (really bad) physics engine. They decided that the best way to show it off would be to cram the game full with retarded physics-based puzzles.
One of these puzzles involved pushing a couple of empty barrels underwater to work as a counter-weight for you car. The problem with this is that to push a crate like that underwater, with the ease that Freeman does it with, you'd have to be Superman or something... Not some physicist...
Great going Valve! How the fuck was I supposed to figure out the Freeman was, in fact, God?