Comparison of density estimates of Nematoda and Harpacticoida obtained by a Van veen grab and SCUBA diving from a sandy sediment in shallow water shows that Harpacticoida are sampled efficiently with the grab but nematoda are not. For the Nematoda, total density is underestimated. and the relative abundance of surface-dwellers is overestimated. Samples obtained with a Van Veen grab from which the material is collected in a bucket and subsampled afterwards have a much smaller statistical variability than samples obtained with other methods. ; Comparison of density estimates of Nematoda and Harpacticoida obtained by a Van veen grab and SCUBA diving from a sandy sediment in shallow water shows that Harpacticoida are sampled efficiently with the grab but nematoda are not. For the Nematoda, total density is underestimated. and the relative abundance of surface-dwellers is overestimated. Samples obtained with a Van Veen grab from which the material is collected in a bucket and subsampled afterwards have a much smaller statistical variability than samples obtained with other methods.