The top photo looks like a single eel, but a closer look shows some color variation. It’s really two Whitemouth Moray Eels. I noticed the first one, with its head on the right of the photo, and took a few photos. Then a second, smaller Whitemouth swam into the picture. It was nearer to me, but then retreated into the crack angling at 45 degrees to the first eel.
It popped out of the other end of the crack, and the two eels looked at each other for a moment. The smaller eel then headed toward the other one, only to be greeted by a nip on the head. Chastened, it retreated back into its crack and that’s the way I left them.