Soils deposited underwater are typical of natural environments such as alluvial, fluvial, and offshore soils, or man-made infrastructure, like tailings dams. The preponderance of this type of deposition have made them a key target of soil mechanics research for many years. This study investigated the behaviour of sandy and silty materials deposited underwater using a comprehensive approach which aims to coordinate and critically analyse experimental and numerical practices from a macro and micromechanics perspective, by trying to evaluate the role of fabric in the soil´s behaviour. A novel setup was presented for the slurry deposition method that simulates underwater deposition, and can obtain high-quality, uniform specimens of sands or silts, the latter of which had never been done before. Mechanical behaviour from specimens reconstituted with this method were compared with the widely used moist tamping method, showing a strong effect on strength and stiffness owing to the initial fabric that results from the reconstitution method. An innovative analysis of the procedures required to establish the critical state line of sands based on small-strain data was also introduced. A new proposal for the assessment of critical states using phase transformation and peak states data was assessed through single element simulations. The use of the optimised calibration approach for the critical state line within a bounding surface plasticity model showed a better than usual performance to model key states of undrained triaxial shearing data over a wide range of densities and effective stress levels. This research also investigated the behaviour of slurry-deposited specimens of sands subjected to cyclic loading. The anisotropic nature of the specimens tested was revealed in monotonic loading, therefore in the boundary that triggered deformations in cyclic loading. The challenges of high-frequency triaxial testing were analysed, and the effects on the test results of inappropriate system performance were presented. The effect of frequency on the results of isotropically consolidated tests carried out with frequencies ranging from 0.1 Hz up to 5 Hz suggested a moderate increase in cyclic resistance as frequency increases for this material and the testing conditions used. Additionally, the study explored the applicability of multidirectional bender element testing in the assessment of the initial fabric and its evolution of granular materials in relation to all previous macroscale investigation factors and features, including the reconstitution method, monotonic shearing, and cyclic loading behaviour. Shear wave velocities in different axes were able to detect consistent differences between methods and distinct variations throughout loading.