I had a near death experience at Sandstone Falls (really Brooks Falls, but I just call it Sandstone).
My dad and were shooting pictures of the falls (basically - short whitewater rapids and a five to ten foot drop). We decided to get closer, thanks to some rocks that got close to river level and were the riverbank itself. I decided to try to take a photo of me dipping my hand in the water (prove that I was in one of the oldest rivers in the world, cause bragging rights). I was on a rock that was half "wet", and I spotted a point on the rock that, if I kneeled, I could dip my hand into the water there. It was much closer to the river than where I was standing.
The issue was that it was in the wet area. I assumed it was just water, and that I wouldn't slip. I tried walking over to the point, and upon entering the wet area, I almost fell to my feet. Luckily, my phone (which I was using as a camera) was in my pocket, and didn't fall out. Had I slipped, I would've either cracked my head on the rock, or fell into the whitewater rapids and get pummeled by the rocks in the falls. I also would've probably lost my phone. Luckily, I didn't, and told my dad that there was a slippery part of rock. My dad told me that it was algae that was near invisible to the eye, and not to stand there.
Lesson learned, so I tried another spot that was dry. I never took the picture, since my dad wanted me to pose in a photo.