Scarus psittacus, commonly known as parrotfish, is named for its parrot-like beak, which it uses to bite off chunks of coral that it crushes and digests. Most of the sediment found on white sandy beaches is parrotfish poop.

Art and fact by Darien Satterfield, Instagram & Twitter & Tiktok @DiverDarien
[Edited by Nicole Rodrigues]
References:
Perry C.T. , Kench, P.S., O’Leary, M.J., Morgan, K.M. , & Januchowski-Hartley, F. (2015). Linking reef ecology to island building: Parrotfish identified as major producers of island-building sediment in the Maldives. Geology, 43 (6), 503–506. https://doi.org/10.1130/G36623.1
Morgan K.M., & Kench P.S. (2016). Parrotfish erosion underpins reef growth, sand talus development and island building in the Maldives. Sedimentary Geology, 341, 50-57. https://doi.org/10.1016/j.sedgeo.2016.05.011