Video over long distances

[m_g]

Hi all,
I am new here, but keen to learn about transmitting video signal long distances and wasn't sure where best to pose this question.

I have a camera with HDMI and composite video out options (for live feed). I would like to transmit this signal approximately 30 metres, but from what I have read, I am likely to experience some(perhaps a lot) of signal degradation.

So my question is, what would be your preference of transmission (hdmi or composite), what other bits of hardware would I need (extenders etc), maybe should I go cat 5? Things to be aware of, quality does not need to be amazing as budget is an issue, but obviously clearer is better. Also, this is for outside work, over and through water, possibly remotely, so any powered options need to be very portable. Since this may be going through water it can't be wireless transmission.

On another note, does the fact the cable may be running through/under water affect how the signal will degrade?

Any help much appreciated.

Cheers

Mg

[jagabo]

HDMI over Ethernet.

Example of cheap baluns:
http://www.amazon.com/HDMI-over-Cat-Extender-Balun/dp/B001CKKX8Q

There are some that can run longer distances. Up to about 100 meters:
http://www.amazon.com/Cable-Matters-Extender-Support-Ethernet/dp/B005H4Y6TA/