The large-scale experiments described herein were carried out at Forschungs-Zentrum Küste (FZK), Hannover (Germany) by a research team of the Universities of Bologna, Edinburgh, Southampton, Plymouth, HR Wallingford and the Coast and Harbor Engineering, Inc. (USA). Wave-induced loads on close-to-prototype jetties were measured. Experimental evidence indicates the presence of force peaks with a short space–time correlation structure, carried by convective processes with a velocity of the order of the wave celerity. The important limitations imposed by the imperfect spatial resolution of pressure transducers on the integrated force are discussed. The finding may be of interest to design laboratory tests involving rapidly-varied processes such as impact waves and the subsequent analysis phase, which may lead to gross errors in the evaluation of the integral process. A guideline to select the cutting frequency is provided