Hi Roger,
The lack of shielding shouldn't be an issue but you must have twisted pairs with suitable characteristics for Ethernet to work. Since it's almost working setting the network to 10 MHz Half Duplex may give better results. 
If you have mains from the same source in both boxes you could try a pair of Homeplug Ethernet-over-mains modems to bridge the gap. If you really want to cheat you might be able to use a wireless bridge and an access point and use wifi between the boxes. 
Cheers,
Paul. 
Sent from my BlackBerry® wireless device
-----Original Message-----
From: Roger Munford <rogermunford@???>
Date: Fri, 27 Nov 2009 16:13:55 
To: <Hampshire@???>
Subject: [Hampshire] Ethernet connection Unscreened
I am working on a project that, at the last moment added an ethernet 
connection, between two water proofed housings about 1 meter apart. 
Within the boxes normal Cat 5 is used but through the housings and 
connecting the two is a rather chunky specialist submarine cable which 
has no shielding and no twisting of pairs. This setup scarcely works but 
it does work a bit. The housings have already been manufactured and the 
connection is a spare unused one which the designers thoughtfully added 
but not with ethernet in mind. Should this sort of degradation be 
expected? Any advice/comments would be gratefully received.
Roger
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