Vibrations of slabs in the.surge shaft chambers of hydroelectric power stations are often caused due to dynamic effect of upsurge and down surge conditions and water hammer effects due to sudden closing or opening of the gates. It is generally feared that if the frequencies of the dynamic forces match with one of the natural frequency of the slab, a resonance condition may arise which may lead to severe amplification of forces. The problem of computation of natural frequency is complicated by the fact that the slab being submerged in water, a virtual mass of water will act with it which is expected to modify its frequency considerably. This contribution of the water can only be determined by model test. This paper presents the results of an investigation carried out by the authors in regard to the vibrations of Surge-shaft slab of Dehar power plant in the Beas-Sutlej Link Project.