The Exquisite Butterflyfish is one of my favorite fish. I have seen them many times in the Red Sea.
Usually two fish swim together.
This fish is also called blacktail butterflyfish (in latin Chaetodon austriacus). It is native to the western Indian Ocean but has reached the Mediterranean Sea as a migrant through the Suez Canal.
Here is one of the lovely closeup photos I managed to capture in Sahl Hasheesh, in the Red Sea.