Thread from the WWn wiki - content originally developed by Andrew
2 Tin-Can Telephone
4 Two Way Radio/PMR/Walkie Talkie
All fields of water warfare involve some degree of tactical analysis, whether it is simply to charge in and soak all in sight, or a complex attack on an enemy emplacement. On any scale of water war involving more than one person per team, good communication can be the difference between soaking, or being soaked. The right comms for the situation depends on many factors, and the best kit for one situation may not be the best for an alternative situation.
 Tin-Can Telephone
Although extremely basic, the tin-can telephone can be extremely useful for quietly and reliably communicating to a forward outpost or other friendly position within a reasonably close range. Although easily portable, this form of communication equipment can take longer to set up than other methods of communication.
Easy to use
Take longer to set up than alternatives
Effective over a reasonably short range only
A useful piece of kit anyway, a torch can be used as an effective signalling device either sending detailed messages or simply as a signal for some pre-determined action to be carried out. Messages can be transferred silently over large distances via morse code and can also be easily encoded if required. Unfortunately if you can see the signal, it is possible that the opponents can also see and intercept it without your knowledge. The signal can easily be used by your opponents to identify your location, especially at night.
Easy to use
Possible to encode messages
Can give your position away
Messages can be easily compromised
Can be rendered useless if not watertight
Slow to send detailed messages
 Two Way Radio/PMR/Walkie Talkie
Possibly the first type of communication device that springs to mind is the Two Way, Personal Mobile Radio or Walkie Talkie. Although more expensive than some other options, these devices are one of the most reliable methods of communicating over larger distances. Most modern PMR's feature security codes and headset possibilties allowing them to securely transmit messages up to or above 10km. There are even completely waterproof PMR's avaialble, greatly reducing the risk of damage on a water warfare field.
Very easy to use
Secure channels available
Waterproof models available
Headset/throat-mic extras available
More expensive than alternatives
Range greatly reduced by terrain features (buildings hills etc.)