I went to a dolphin show at the Vancouver Aquarium a few years back and wandered near the dolphin pool after the show. I saw one dolphin playing with what looked like a tiny piece of thread that accidentally fell into the pool. He was spitting it out, watching it dance through the water, quickly sucking it in only to spit it out and watch it wiggle, over and over. He was just entertaining himself and having a good time.

They're incredible animals.