Abstract—In this paper we consider inter-robot commu- nication in the context of joint activities. In particular, we focus on convoying and passive communication for radio-denied environments by using whole-body gestures to provide cues regarding future actions. We develop a communication protocol whereby information described by codewords is transmitted by a series of actions executed by a swimming robot. These action sequences are chosen to optimize robustness and transmission duration given the observability, natural activity of the robot and the frequency of different messages. Our approach uses a convolutional network to make core observations of the pose of the robot being tracked, which is sending messages. The observer robot then uses an adaptation of classical decoding methods to infer a message that is being transmitted. The system is trained and validated using simulated data, tested in the pool and is targeted for deployment in the open ocean. Our decoder achieves .94 precision and .66 recall on real footage of robot gesture execution recorded in a swimming pool.