Byrrhoidea (Pill, water and toe-winged beetles)

The superfamily Byrrhoidea includes a number of beetle families, most of which are either aquatic or associated with a semi-aquatic habitat. Other than the superfamily Hydrophiloidea, the majority of the remaining Polyphagan beetles which are aquatic are in this superfamily. These families were traditionally grouped as a separate superfamily, the Dryopoidea, which is no longer recognized. The vast majority of species are small (<1 cm), and predominantly dull brown or black.

— Wikipedia