.the not-so-giant rock!
Yes, that rock is alive. It's called Pyura chilensis - "piure" for short in Spanish. It's part of the extremely weird group of creatures called tunicates/sea squirts- primitive vertebrates that are free-swimming when young, then become stationary blobs as adults. In this case, the blob looks like a giant rock and lives off the coast of Chile and Peru. As with all other mature tunicates, it is a filter feeder, feeding on any microorganisms that find their way into its rocky, yet surprisingly squishy insides before squirting that water back out.
Yeah, maybe it's time for a refresher on what a tunicate is. Tunicates, sea squirts, and sea salps are, collectively, the weirdest chordates in existence. They start life as free-swimming, tadpole-like creatures with brains, spines, and other very vertebrate traits. When they mature, however, they change entirely, eating their primitive spinal chord and becoming little more than jellyfish or sponges. In this case, the piura becomes a living rock as an adult. Can it have the "best camouflage ever" award? It pretty much ate its brain for it.
Like all tunicates, the living rock is a sequential hermaphrodite. It's born male, then becomes female as it gets older.When it's on the edge of becoming female, it releases both sperm and eggs into a messy cloud in the water. Yes, the living rock can effectively mate with itself if the need arises. Consider your mind blown.