The invention relates to a trailer that is especially used for moving over very soft ground and for launching lightweight boats, comprising a motor-driven supporting running gear (11) designed to hold the hull of the boat and extended by a longitudinal edge (12) ending in a lift jack (13) comprising a maneuvering handle (132). The supporting running gear (11) comprises an essentially tubular frame (111) arranged transversely to the longitudinal axis of the trailer, and to which a sealed differential-motor reducer unit (14) or an electric motor could be fixed.