In this article, natural frequencies of variable stiffness composite laminate (VSCL) plates with curvilinear fibers submerged in fluid with different depths of submersion are studied. In each layer of VSCL plate, the fiber-orientation angle changes linearly with respect to the horizontal coordinate. The problem is solved by using the hierarchical finite element method (HFEM) (p-version), with seven degrees of freedom per node and the higher-order shear deformation theory (HSDT) for C⁰ continuity. The plate theory ensures a zero shear–stress condition at the top and bottom surfaces of plate and does not require a shear correction factor. The fluid/structure interaction is examined in this study, in which the effect of fluid is assumed as pressure acting on the plate. The mathematical model of fluid is given by employing velocity potential and Bernoulli equation. The obtained frequency parameters shown an excellent agreement when compared with experimental and analytical results of available solutions in literature. Accurate results are obtained by increasing the degree of polynomial shape function of HFEM. In order to examine the effect of fluid on VSCL plate, different cases are studied to find out the effect of plate thickness, curvilinear fiber angle and depth of submerged plate.