Since you are completely alone (or so you think) you decide to go for a swim. You remove your clothes and pile them on a large rock by the water then wade in. The water is cool and clear - quite refreshing on this warm summer afternoon. Once you are deep enough, you dive underwater to really cool off. There is a steady current from the waterfall, but not a strong one so you can easily swim against it. You swim toward the waterfall then drift across the pond without a care in the world.
After maybe a half hour of swimming, floating, and generally relaxing in the pond you think perhaps you should head back to your cabin. You stand up in the pond in an area deep enough that only your head and shoulders are above the surface. That's when you get an odd feeling...