It might have just been the angle, or the lighting, but I definitely saw it...a fish smile. 

We were snorkelling and I was hanging around an underwater cave, waiting very still for my sister to give me my GoPro. Whilst I waited, I watched the different coloured fish, each prettier than the last. As I was doing so, I saw a fish that looked strangely chilled out and relaxed, as if he had nothing on his mind. He was very beautiful, but for some reason he looked as if he was my friend, and then I saw it. His mouth open curled into an unmistakable smile. His scales rusty orange and brown glistening in the light that shone through the water. But as soon as he had come, he had gone. That was enough to cheer up the rest of my day.