Some signals have multiple meanings which become obvious in context. There is a breakdown of common signals used by the Tsunami Rangers at sea in the table available here. These comprise the bulk of signals that we use most often. Occasionally we add new ones or drop ones that have no use. We are open to learning new signals that have value or are simply clearer than extant signals.
All signals use only one hand.
You might then salute your comrade, point to the horizon, point to him, do a seig heil, and then raise your palm up. And everyone lives happily ever after. The above example illustrates a sample scenario at sea. Everyone speaks a little differently to communicate the same thing. As long as everyone understands every time, there is no problem.