The investigations of sediment movement with the use of radiotracers have been carried out in a surf zone of Lubiatowo. Inception of sand motion and sediment transport velocity were the objective of the experiment. The “spider” type construction was located at the depth of 0.7 m. An artificial sand made of iridium glass (γ = 2.660 kg/m3) containing 0.25 weight per cent of192Ir was used as a tracer. Fraction 0.15 … 0.20 mm have been chosen as the representative diameter of sand grains existing at the investigated bottom region. The inception of sand movement vs current velocity and wave conditions as well as displacement velocity of tracer mass were determined. The new improved construction, “spider II”, was designed and tested.