Such connections are very difficult to make at {TAIL ~ great depths} of a plurality of hundreds of {HEAD ~ meters}, with the difficulty increasing at increasing depths 
Such connections are very difficult to make at { TAIL ~ great depths } of a plurality of hundreds of { HEAD ~ meters } , with the difficulty increasing at increasing depths
OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH