Built for the The Eagle Oil and Shipping Co Ltd., London the steel steam tanker San Tiburcio was launched from the yard of Standard Shipbuilding Corporation, New York on 29th January 1921. She measured 413.0′ x 53.4′ x 31.1′ and weighed 5995 gross tons, 3618 net tons. Her triple expansion steam engine by Sun Shipbuilding Corporation, Chester PA delivered 544 nhp.
The San Tiburcio spent most of her working career shuttling back and forth between Mexico and California carrying loads of Californian crude oil to the refineries of Mexico and, despite several lean years as her owners managed their way through the desperate times of the Great Depression in the 1930s, the ship had done well for the Eagle Oil Company. However with the outbreak of the Second Word War all this was to change. Desperate for carrying capacity for fuel to keep the British war effort afloat many dozens of tankers under British ownership were requisitioned or chartered by the Ministry of War Transport to keep the fuel supply lines flowing. The San Tiburcio was one of these ships.
And so, it was on this duty, that the San Tiburcio set out from Scapa Flow under the command of Captain W F Flynn with a crew of 39 men and a cargo of 2193 tons of fuel oil. She was bound for the other important naval base in the area at Invergordon on the Cromarty Firth. She sailed south, out through the boom at Hoxa Sound, across the Pentland Firth and was soon heading south down the Caithness coast towards Cromarty through the well marked swept channel that guided ships through the dangerous, potentially mined, waters in the area. She soon reached the Dornoch Firth and was closing in on her destination when disaster struck.
Three months earlier, on February 9th 1940, the German mine laying submarine U-9 commanded by Wolfgang Loth, had managed to evade British patrols and laid her deadly load of mines directly off the entrance to the naval base at Cromarty. The San Tiburcio steamed full ahead directly on to one of these mines and a huge explosion ripped through the steel hull plates of the tanker. Within 45 minutes of the impact the ship started to break in two although, thankfully, the two parts remained afloat long enough for the crew, who had luckily managed to avoid injury in the explosion, to safely abandon ship. Shortly after the two sections sank beneath the waves.
The wreck of the San Tiburcio lies in two pieces in position 57° 46.548’N, 003° 45.619’W (WGS84). Both sections sit upright and fairly in tact on a flat seabed some 30 metres apart although both are now disintegrating as the sea eats its way through her steel hull plates. The bow section, which is approximately 50 metres long, lies to the south in 35 metres of water with the stern section, which is around 70 metres long, lying at right angles to the bow section. On both sections the superstructure, while crumbling, is still visible and the extreme front and rear ends of the ship, furthest from the damage caused by the explosion and subsequent ripping apart, are the most in tact portions of the wreck.