A polymer coating applied to the wet surface of a ship’s hull can reduce some types of damage to a ship subjected to a far-field underwater explosion (UNDEX). The polymer coating is a thin wall structure which applied to the wet surface of ship hull, but the ship is a relative large structure. The dimension mismatch between the coating and the ship results in difficulties in the simulation, and even that it is not feasible to mesh the detailed core geometry. Hence, an approximate simulation method for the full-scale ship with polymer coating is developed. Based on the homogenization theory of polymer coating, a continuum model which takes into account the strain-rate dependence is introduced in the full-scale ship model. The shock response subjected to UNDEX of the finite element ship model is investigated. In order to investigate the effectiveness of such coatings in blast-resistant design, full-scale UNDEX tests for a ship with and without polymer coating are performed. The results obtained from UNDEX tests and numerical simulation are compared and discussed. The blast-resistant property of polymer coating is elaborated.