On October 11, 1918, a devastating earthquake and tsunami struck Puerto Rico. One hundred years later, the debate on the source of this event continues. Until recently, many scientists agreed that the earthquake originated in the Mona Canyon and that the tsunami was a direct consequence of the earthquake rupture. However, reports of ruptured submarine telecommunication cables in the Mona Canyon in 1918, as well as the identification of landslide scars, deposits, and faults in other locations, have led to alternate proposals of the source of both the earthquake and tsunami. One of the objectives of the Océano Profundo 2018 expedition was to explore the deep-sea geology around Puerto Rico in order to shed some light on this enigma.