in 1912, the Titanic left Cobh as it's last port of call before heading across the Atlantic on it's first and only tragic voyage. There is a heritage walking tour in Cobh called the Titanic Trail that might be of interest to visitors. I didn't take it as i didn't have the time.
The Lusitania was a ship that was torpedoed and sunk 30 miles or so off the coast of Ireland near Cork in 1915. Many of the dead are buried in the Old Cemetery here.