On the afternoon of April 24, 1917 the Italian sailboat Bien Aimé Prof. Luigi was on a route between the UK and Genova, Italy.
As the boat sailed past Sagres the crew was unaware that since 06.30 a German imperial submarine, the U-35 commanded by Lothar von Arnauld de la Perière was shadowing the Bien Aimé Prof. Luigi, a sailboat built to carry cargo, built in 1907.