The transportation off‐shore of the littoral pycnogonidNymphon gracileduring the winter months is facilitated by the ebb tide swimming of this otherwise benthic animal. The energy cost of migration has been estimated from measurements of oxygen consumption and drag forces acting on the different segments of the leg during swimming. The swimming patterns ofN. gracileboth under constant conditions and in response to tidal pressure cycles are considered in relation to the animals' energy reserve