Wave concentrators have significant value for ocean energy absorbers to reduce power generation costs. Besides, the protection problem of the concentrator itself should also be carefully considered. In this study, a self-protected energy concentrator (SPEC) for water waves consisting of several truncated cylinders arranged in a concentric circle is proposed by adopting the cloaking technology based on the idea of manipulating scattered waves. To design the SPEC, an optimization program built by a combination of the higher-order boundary element method, the wave interaction theory, and the real-coded genetic algorithm is utilized. To address the manipulation mechanism of the scattered waves as well as to investigate the performance of the SPEC against various wave steepness and a spectrum of waves, the scattered waves and the total waves both inside and outside the concentrator are numerical and experimentally analyzed. High energy density inside the concentrator and the self-protection of the concentrator are validated. It is found that the large wave steepness can reduce the efficiency of concentration and self-protection due to the wave breaking. The SPEC has a high performance at a moderate bandwidth. Besides, the wave frequencies perform a more significant effect on self-protection than the concentration characteristic.