The control of a swarm of underwater robots requires both a control algorithm and a communication system. Unfortunately, underwater communications is difficult at the best of times and so large time delays and minimal information is a concern. The control system must be able to handle a large number of robots without a master control, i.e., a decentralized control approach. This paper describes Consensus control as a way to decentralize. Consensus control allows each robot to know the final goal and then to decide, based on the position of the other robots, its best move to help achieve the goal.