To operate a shell being a vibration part of the underwater wave transmitter-receiver smoothly and to operate the underwater wave transmitter- receiver without being affected by the depth in use.

In the underwater wave transmitter-receiver consisting of a cylindrical shell 1 vibrated through vibration from a drive section or in water, a cover 2 covering an opening of the shell 1 and a spacer 5 interposed between the shell 1 and the cover 2, a projection 6 is formed to the side of the shell 1 of the spacer 5 along the outer circumference of the spacer 5 and the projection 6 is in contact with the shell 1.