The discovery was no small feat. After a persistent search that spanned several years, the submarine, which had been lost to the depths since November 1917, was identified through diligent research, underwater surveys and the collation of historical data. 

SM UC-18 was a German Type UC II minelaying submarine or U-boat in the German Imperial Navy (German: Kaiserliche Marine) during World War I. In six patrols, UC-18 was credited with sinking 34 ships, either by torpedo or by mines laid. UC-18 was sunk by the British Q ship HMS Lady Olive on 19 February 1917. These two vessels allegedly destroyed one another in a famous WWI battle. It is the only known altercation where a submarine and a Royal Navy ship sank each other.

Lying in more than 70m of water, the wreck of UC-18 and that of which the divers believe to be HMS Lady Olive have been located 40 miles west of their historically recorded position of 12 miles south of Guernsey. 

The find has been filmed for a BBC documentary that will air on the BBC in June. Underwater filmmaker Karl Taylor told the BBC that he was elated by the find and the project had been "very demanding" with deep dives in very low light.

French authorities have since closed the UC-18's location to divers as it is a designated war grave.