We have investigated the influence of fluoroplastic, copper, and silicon carbide inert inserts on the process of detonation transmission through water. Active and passive HE charges were molded from Comp B. On the rear end of the passive HE charge an identification steel specimen was mounted, which detected presence or absence of detonation. Inert inserts were shaped as square prisms of varying lengths, and were contained between active and passive HE charges without any clearance on the way of initiating shock wave with partial overlap of HE cross sections. It is shown that preloading of a passive HE charge with a shock wave transmitted through copper or ceramic inserts causes considerable desensitization of the Comp B. Ceteris paribus, the crash distance of detonation transmission for copper was equal to 74%, and for silicon carbide – to 60% of the distance for fluoroplastic. While performing the experiments with ceramic inserts we have observed cumulation phenomenon, which manifested itself as a hole in identification steel specimen with depth of about 10 mm. The surface of specimen had typical temper colours that demonstrated presence of high temperatures.