sentences:  The patrol made several sightings of a submarine, but did not manage to bring it to action before a shortage of hydrogen for the balloons on 8 July forced the flotilla to return to Scapa Flow.On 11 July, "Patriot" set out as part of another sweep by kite balloon equipped destroyers against German submarines.On 12 July, the observer aboard "Patriot"s balloon spotted a submarine on the surface.