Power was provided by a dual diesel/electric system. Whilst on the surface, two 400 horsepower Paxman diesel engines drove the two propellers via the two generators which ensured the main battery remained fully charged. The Umpire carried 38 tons of diesel fuel, this giving her a range of 3,800 nautical miles at 10 knots whilst surfaced. When submerged, the propellers were driven by two electric motors of 825 horsepower supplied directly from the main batteries consisting of 112 high capacity cells, these being situated beneath the control room and accommodation space. The time that was able to be spent underwater was dictated by the charge held in the batteries, in turn the time spent underwater was not infinite , this meaning the submarine would have to surface periodically and run on her diesel engines in order to recharge their batteries. 

During the war years the U Class boats proved themselves to be very capable in both the North Sea and the Mediterranean .  A further 34 boats were ordered in 1940 and 1941. These vessels, the third group built were lengthened by five feet in order to provide a more streamlined shape. In all 49 U Class boats were built. The Umpire was seven months out of her builders hands when she sank.

At the time of her collision with HMT Peter H Hendricks, whilst running on the surface, four crew members were conning the tower. Of these only one survived. The remaining crew, trapped inside the Umpires hull went to the bottom with her.  Some of those trapped inside of the Umpire made their escape via the conning tower hatch and engine room hatch with the use of the DSEA (Davis Submerged Escape Apparatus). Of the crew, 22 lost their lives.

Today the wreck of the Umpire sits on a sandy seabed at 18mtrs. In good visibility she makes for a spectacular dive. The wreck lies hard over on her starboard side (port side facing skyward). The Umpire has been quite heavily salvaged, with sections of her hull opened up as if with a tin opener. Despite this, for the most part, she is still very recognizable as a submarine.

Starting at the stern you will find the rudder, here also you will find the port prop shaft and port plane. There are no propellers to be seen, as these would have been removed during salvage operations. The extreme stern of the wreck has broken away from the main wreckage, from the break the hull then becomes more structured. Swimming along the hull you will come to an area of batteries, these being used to power the electric engines when submerged. At this point can also be seen one of her two diesel engines, this still being in situ within the Umpires broken hull. A short distance forward of the engine area the hull becomes very broken and collapsed, this being where the main control room would have been, this being situated beneath the conning tower. The conning tower today is no more than a few broken plates laying slightly off the wreck half buried in the sandy seabed. Just off the wreck at this point you will find the mount for her 3 inch gun, however there seems to be no sign of the gun itself, this being either salvaged or buried in the sand, Continuing along the hull with the upright deck to your left and heading towards the bows you will come to the torpedo loading hatch, this is a sloped tube angled forward into the deck, through which torpedoes would have been fed down into the torpedo room. Forward of the torpedo loading hatch is the forward escape hatch, this being open. From here on in towards what is left of the smashed up bows you will pass various pieces of wreckage including the anchor winch. The bow is for the most part unrecognizable apart from the torpedo tubes that are now visible due to the lack of bow plates, these now laying half buried in the surrounding seabed.