Some of the fish that lives on reef shares the same features as those that live On the sand. They do not have a swimbladder, which means they will sink as soon as they stop moving. And many of the species on the reef also prefer to stay unseen. Their coloring mask their profile outline, so it is difficult to acknowledge it is a fish. You find this in e.g. the Greasy grouper in the book. But the scorpionfish takes it a step further, and having extrusions that resemble algae growth on the reef, and blur the outline of the body even more. It helps many of them in their hunt for food: they sit completely still until a small fish is near, then they shoot up/out against the prey in an explosion.
They can be really difficult to see! So, you may not notice them until you make a deliberate search for them. E.g. the small pipefish. They are actually quite common – even in shallow water reefs (0.5-2 meters) as long as it is fairly sheltered. But also large scorpion/stone fish can be hard to find. I have many times been surprised to see a 40-50 cm long fish right in front of me. Only noticing it because I was there to take pictures of e.g. a damsel nearby…
As shown in the book, the Freckled hawkfish can be found in two distinct patterns. I have actually not been able to find out if the same individuals can change between the two patterns or if they grow up getting one or the other pattern.
Other fish have different patterns or colors e.g. the Blacktip grouper may look quite different from the image in the book (see below).