Parrotfish are very colourful. Their name comes from the parrot-like beak formed by their teeth. The buccal cavity (cheek) of the parrotfish secretes the 'sleeping sack' that the fish sleeps in overnight. It is a semi-translucent sack which completely surrounds the parrot fish. In the morning the sack is discarded. You can see these on the sea bed floor during the following day.