Communications system

1. An underwater communications system comprising:

an electromagnetic transmitter which transmits electromagnetic and/or magnetic signals to a remote receiver and a data input said electromagnetic transmitter comprising a modulator for modulating input data onto a carrier signal; and

a plurality of electromagnetic transceivers each having a network transmitter and a network receiver wherein at least one of said electromagnetic transmitter and said remote receiver is underwater and the plurality of electromagnetic transceivers form a mesh network operable to act as a communication link between said electromagnetic transmitter and remote receiver,

wherein said electromagnetic transmitter, said remote receiver and said electromagnetic transceivers are operable to communicate within a near field of said electromagnetic and/or magnetic signals, said near field of said electromagnetic and/or magnetic signals corresponding to a region around said electromagnetic transmitter where at least one of inverse distance squared (1/r 2 ) and inverse distance cubed (1/r 3 ) field components of said electromagnetic and/or magnetic signals is greater than an inverse distance (1/r) field component thereof.

2. The underwater communications system of claim 1 , wherein said electromagnetic transmitter further comprises an electrically insulated, magnetic coupled antenna for transmitting the electromagnetic signals.

3. The underwater communications system of claim 1 , wherein said data input includes at least one of: a text input; an audio input for capturing audio signals; an image input for capturing an image and a video input for capturing a video image.

4. The underwater communications system of claim 1 , wherein said remote receiver comprises an electrically insulated, magnetic coupled antenna for receiving said electromagnetic and/or magnetic signals and a demodulator for demodulating said electromagnetic and/or magnetic signals.

5. The underwater communications system of claim 1 , wherein each said network transmitter further comprises an electrically insulated, magnetic coupled antenna.

6. The underwater communications system of claim 1 , wherein periodic transmission of data occurs when relevant new data is available at the electromagnetic transmitter.

7. The underwater communications system of claim 1 , wherein periodic transmission of data occurs upon receipt at the electromagnetic transmitter of a send request issued by the remote receiver.

8. The underwater communications system of claim 1 , said electromagnetic transmitter further comprising a digital data compressor for compressing data that is to be transmitted and said remote receiver further comprises a digital data decompressor for decompressing said compressed data.

9. The underwater communications system of claim 1 , wherein said electromagnetic transmitter is operable to transmit signals having a frequency in the range of 1 Hz to 100 MHz.

10. The underwater communications system of claim 1 , wherein at least one of the plurality of electromagnetic transceivers is above water and is operable to pass a signal from said electromagnetic transmitter to said remote receiver through an air propagation path.

11. The underwater communications system of claim 1 , wherein at least one of said plurality of electromagnetic transceivers is mobile.

12. The underwater communications system of claim 1 , wherein at least one of said electromagnetic transmitter and said remote receiver is an above water station.

13. The underwater communications system of claim 12 , wherein said above water station comprises an electrically coupled antenna.

14. The underwater communications system of claim 1 , wherein at least one of said electromagnetic transmitter and said remote receiver includes a device for varying a signal gain.

15. The underwater communications system of claim 1 , wherein said electromagnetic transmitter and said remote receiver are both located underwater, and wherein said electromagnetic and/or magnetic signals follow a signal path which is at least partially an air path that is above water.

16. The underwater communications system of claim 1 , wherein said electromagnetic and/or magnetic signals follow a signal path which is at least partially through a sea bed.

17. An underwater communications system comprising:

at least one transmitter and at least one remote receiver and a plurality of transceivers, a first transmitter of said at least one transmitter comprising:

a data input;

a modulator for modulating input data onto a carrier signal; and

an antenna operable to transmit modulated electromagnetic and/or magnetic signals to a remote receiver,

and a first remote receiver of said at least one remote receiver comprising:

an antenna for receiving said transmitted electromagnetic and/or magnetic signals, wherein at least one of the first transmitter and/or the first remote receiver is underwater and transmission of data between the first transmitter and the first remote receiver occurs via a mesh network formed of the plurality of transceivers,

wherein said first transmitter, said first remote receiver and said transceivers are operable to communicate within a near field of said electromagnetic and/or magnetic signals, said near field of said electromagnetic and/or magnetic signals corresponding to a region around said first transmitter where at least one of inverse distance squared (1/r 2 ) and inverse distance cubed (1/r 3 ) field components of said electromagnetic and/or magnetic signals is greater than an inverse distance (1/r) field component thereof.