A navis lusoria (from Latin, meaning "dancing/playful ship", plural naves lusoriae) is a type of a small military vessel of the late Roman Empire that served as a troop transport. It was powered by about thirty soldier-oarsmen and an auxiliary sail. Nimble, graceful, and of shallow draft, such a vessel was used on northern rivers close to the Limes Germanicus, the Germanic border, and thus saw service on the Rhine and the Danube. The Roman historian Ammianus Marcellinus mentioned the navis lusoria in his writings, but not much about it could be learned until the discovery of such boats at Mainz, Germany in 1981–82.