Here's a common mistake: The subject is lost in the clutter. In this case, Mr. Moray is hard to find against the background of the reef substrate. As Robert Cappa said "if your pictures aren't good enough, you're not close enough".
Sometimes when shooting wildlife, however, the subject won't let you get close enough. This is one of the times when I wish I had a housed SLR with a long lens. With a single lens reflex you can focus accurately, even with high magnification lenses. That means that you can get a frame-filling shot without physically getting too close.
Note 1. Robert Cappa
was a Time-Life photographer back in the day, best known for his D-Day photograph of The Face in the Surf
. He died after stepping on a land mine during the 1st Indochina, or French-Vietnam War, proving that there's a fine line between "not close enough" and "too close".