After Berry sued in district court, the defendants voluntarily paid her the full amount they owed her, including penalties and interest, and sought to dismiss the case as moot. Attorneys’ fees are ancillary to the underlying action, and the existence of an attorneys’ fees claim does not resuscitate an otherwise moot controversy. The panel held that Berry was not entitled to fees under 33 U.S.C. § 928(a). She did not “successfully prosecute” her claim because the defendants’ voluntary conduct mooted the case, and Berry obtained no judicially sanctioned relief in the district court. The catalyst theory was not available under § 928(a).