This study examines the impact of fluid presence on the dynamic characteristics of thin elastic circular plates. Numerical analyses were conducted alongside experimental measurements, focusing on the free vibration characteristics of a clamped circular plate under in vacuo and partial fluid contact conditions. The experimental setup consisted of a circular end plate mounted on a rigid cylindrical tank, with clamped boundary conditions ensured by closely-spaced bolts. The numerical approach, based on linear hydroelasticity theory, was developed in two phases. First, in vacuo dynamic characteristics were analyzed using the NURBS-based isogeometric finite element method (IGAFEM). Next, the fluid environment was introduced, incorporating generalized in vacuo modal displacements as boundary conditions in a potential flow model. Fluid-structure interaction effects were represented by fluid-added mass terms, with fluid forces for each mode calculated using the NURBS-based isogeometric boundary element method (IGABEM). The results demonstrated significant alterations in the dynamic response due to fluid presence. A strong correlation between experimental and numerical results was observed, with natural frequencies and mode shapes showing favourable agreement.