Twenty-year-old Adrian Lynch disappeared after a work Christmas party in December 2015.
Despite one of the most extensive and high profile police searches, what had happened to him remained a mystery until workmen discovered a body in the water at Handois Reservoir in early August.
Police were able to confirm it was Mr Lynch because his passport was in one of his pockets, and through dental and DNA tests.
Family, friends and those involved in the search attended a memorial service for Mr Lynch at the Methodist Centre in mid-August.