Pressure waves, generated different points along radial runs on the continental shelf and slope south of Long Island by 1‐1b explosions of TNT, were received by hydrophones connected by sea cables to a fixed station in the ocean. An extensive analysis of the dispersion phenomenon in the water wave covering five radial courses within a 150‐mile radius of the receiving station was made. Nearly 500 charges were examined in this analysis, and the “seasonal” effect upon dispersion was investigated. In general, for shallow water the received pressure wave displays certain features that are characteristic of the depth of the water, the velocity‐depth contour in the water, the range, and the structure of the bottom. Dispersion in the water wave was also observed in a surface channel formed in moderately deep water. The observed dispersion phenomena were studied quantitatively, and the data were interpreted in terms of the bottom structure. Two‐ and three‐layer liquid models were employed to interpret the experimental results. An expression is presented that relates all the parameters pertinent to the dispersion phenomenon.