That's a moray.
This video documenting a professional diver's unlikely friendship with a moray eel is so oddly heartwarming, I may have to stop eating sushi made with eel. At the very least, I'll ask the waiter if the fish happened to be from Indonesia and had a friend named Valerie.
That would be Valerie Taylor, who first met "Honey" the eel back in 1974 while diving near Banda Island, Indonesia. She began feeding the curious fish other fish and over time the two developed a bond. Valerie says that after a few years of regular visits, as soon as Honey spotted her diver pal, she would swim out of her cave to greet her, and the two would cuddle.