Stopped and found water leaking

Filled car up with water again and started. And the thing still pours water all over the ground!
After a couple of hours digging around the back of the block i find what appears to be the leak. there is a metal pipe that runs from thee water pump, down the drivers side of the block, around the back of the block to half way up the other side! the pipe must have a crack or pin-hole in it. (Cant feel any damage with my fingers)
from a pic when doing my clutch, this is what the pipe is i think

now the ways of fixing it i see are either removing the gbox and cutting the pipe out and joining a replacement bit in. or removing the pipe it self. removing the pipe itself would involve removing of the intake manifold and the turbos etc. of the two options both are a bitch.
Just fixing the leak wouldnt check the rest of the pipe for damage... which could be bad later on.
Anyone had anything else similar happen, or know what causes it?
Or can suggest a alternative way of fixing it?