In ocean-bottom seismic and vertical-cable surveying, receiver stations are stationary on the sea floor while a source vessel shoots on a predetermined grid on the sea surface. To reduce exploration cost, the shot point interval often is so coarse that the data recorded at a given receiver station are undersampled and thus irrecoverably aliased. However, when the pressure field and its x- and y-derivatives are measured in the water column, the nonaliased pressure field can be reconstructed by interpolation. Likewise, if the vertical component of the particle velocity (or acceleration) and its x- and y-derivatives are measured, then this component can also be reconstructed by interpolation. The interpolation scheme can be any scheme that reconstructs the field from its sampled values and sampled derivatives. In the case that the two fields' first-order derivatives are recorded, the total number of components is six. When also their second-order derivatives are measured, the number of components is 10. The properly interpolated measurements of pressure and vertical component of particle velocity from the multicomponent measurements allow true 3D up/down wavefield decomposition (deghosting) and wave-equation demultiple before wave-equation migration.