A new species, the Seth Forest water scavenger beetle, Hydrochus spangleri Hellman (Coleoptera: Hydrophiloidea: Hydrochidae), is described and illustrated; notes on its biology are included. Known since the 1970's from a single large, vernal pool in Talbot County, Maryland, this apparent Delmarva endemic became a subject of interest and concern when human destruction of its unique habitat in 1982 left the survival of the species open to question. Surveys of depressed wetlands throughout the Delmarva Peninsula during 1997–2002 led to the rediscovery of the beetle at five vernal pools, including the type locality, although abundance there is now relatively low. The pools are all confined to two small forest fragments in Talbot County situated in a predominately agricultural and residential landscape. An additional record, represented by a single specimen collected in 1982 from New Castle County, Delaware, was found in the University of Delaware collection; however, the exact loaction of this site is uncertain.