On 2 March 1918, the Master of SS Rutherglen reported that his vessel had rammed a submarine (which he thought was a U-boat) whilst transiting the Irish Sea. The submarine was crossing his bow at high speed. After the collision, cries were heard, and men seen in the water and there was a strong smell of petrol.

It was decided that Rutherglen should not be informed that she had rammed a British submarine as merchant vessels were encouraged to attack U-boats at every opportunity. The submarine was lost with All Hands and is believed to have been HMS H5 (Lt A W Forbes). A plaque commemorating those who died was dedicated on Armed Forces Day 2010 in Holyhead.