A communications device for use under water by a human speaker. A tubular base member has a mouthpiece located at one open end thereof and an inflatable air bag mounted about another open end thereof. In use, the speaker places the mouthpiece around his mouth to form an air seal therebetween and blows into the air bag to partially inflate it. When so inflated, the speaker talks into the device with voiced sounds being transmitted to the surrounding water through suitable transmitting means attached to the base member, preferably the air bag itself. During talking, the air bag receives and returns the air used by the speaker, thereby effectively preventing the escape of air bubbles from the device which otherwise interfere with communications. The air bag is preferably an elongated, flexible balloon which can be stretched into an extended position when speaking into it under water.