This paper presents the results of soil investigation in soft, normally consolidated organic soil in the estuary of Vistula river. The analysis concerns clayey mud and peat layers interbedded with loose to medium-dense sands. Several Cone Penetration Tests with pore water measurement (CPTU), Dilatometer Tests (DMT) and Field Vane Tests (FVT) were performed on the testing site. The cone factor Nkt was estimated using the results of FVT and peak values of undrained shear strength. The proposition of Nkt change due to normalized Friction ratio (Fr ) has been given. The possible value of cone factor NΔu for organic soils was also suggested. The undrained shear strength of Jazowa clayey mud and peat have been compared with DMT estimates proposed by various researchers. Finally, the structural soil sensitivity of Jazowa deltaic soils was determined on the basis of residual shear strength obtained from FVT and the measurements of sleeve friction.