Various kinds of surgeonfish and wrasse often join shoals of yellow tang (which are also surgeonfish). These are orangeband surgeonfish. Up close, the orange band looks like the bold application of a thick layer of paint.

In my attempts to identify what I see in the water, I use John P. Hoover’s book The Ultimate Guide to Hawaiian Reef Fishes, Sea Turtles, Dolphins, Whales, and Seals. His website is hawaiisfishes.com.