Coating system of a seawater storage tank failed during service at the humid south gulf coastline. The failure occurred during the summer of 2022 after only 14 months of service. The tank had an acknowledged life expectancy of 15 years. An investigation team was deployed to investigate the root causes of the coating failure. In this case study, a comprehensive investigation was conducted to discover the reasons behind the premature failure of the sprayed PU (polyurea) elastomer coating on a water storage tank during a turnkey project in the Arabian Gulf region. Visual inspections alongside longitudinal seams of shell courses revealed rust stains as well as blistering and delamination. DFT (Dry film thickness) checks revealed thickness variations beyond specified limits. Pull-off adhesion tests on the as-applied coating revealed inter-layer (i.e., cohesive) failure. In addition, the holiday checks revealed pin-holes near longitudinal weld seams. On the other hand, the FTIR (Fourier-transform infrared) spectrum of the applied coating was found in close resemblance with the polyurethane spectrum. Whereas, the water resistance test did not reveal significant deformation. The failure mechanism leading to the in-service failure of the applied coating is explained.