I'm not talking in a general sense about aggressiveness by animals in nature. I'm referring to the specific scenario stated where a nurse shark lunched on some lobsters that were 15' away from the diver. Aggressive behavior usually is directed towards someone or something. I didn't see anything in the story about the nurse exhibiting any behavior other than seeing a free lunch and taking advantage of it. Predatory, maybe, but I don't think predatory implies aggression, but that could be argued too.
I guess the lobsters' view may be different
but then we'd have to label everyone at Golden Corral as predatory and aggressive.