Psephenidae

Psephenidae is a family of aquatic beetles in the order Coleoptera, commonly known as water-penny beetles, comprising 273 species in 35 genera found on every continent except Antarctica across tropical and temperate regions. The larvae, which resemble tiny pennies, typically feed on algae growing on rock surfaces and serve as indicators of water quality, since they cannot tolerate pollution or excessive algae and sediment buildup, so their presence signals healthy water conditions. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/