Provide a sense of scale. The jolt of seeing some tiny piece of a strange critter in macro photography is part of the power of this type of picture. A picture of this octopus on the gravel bottom wouldn't be the same. But a photo of this little guy near clam shells or kelp would also provide a sense of scale. People add interest.
Divers interacting with sea life make some of the best scuba pictures.
But you'll find that, between your dive buddy and the fish, it's easier to get the fish to do what you want. But add a diver, and suddenly the picture has emotion and meaning. Look for unusual lighting. Shadows and highlights can be used to make the picture more interesting. By moving your strobe, you can add drama or highlight missed details.