SearchResearch (5/6/2026): What is this called and why do they do that?

I've been busy... Spanish hogfish (in front), followed closely by a Trumpetfish. Why? ...not just with work, but with another dive vacation. And the vacation causes me to be curious about all kinds of things. In this case, there's a peculiar behavior that I've seen multiple times. Two fish of different species will often swim in perfect formation, like two fighter pilots flying in tight formation…