The thirty-six Tamils massacred by Sri Lankan navy officers on board the Kumuthini boat on May 15, 1985 were remembered on Tuesday in Neduntheevu.
Families of those who were killed came to the memorial to light candles and lay flowers in memory of their loved ones.
Eye witnesses reported seeing six Navy officer boarding the Kumuthini boat in plain clothes and pointing a gun at passenders before ordering them to come up to the main deck one by one and shout their name and destination.
Each passenger was then hacked to death. Witnesses reported seeing hacked body parts and blood across the deck.
Amnesty International identified 23 of the victims and recorded eye witness accounts of those who survived the massacre.
The Sri Lankan minister for national security at the time, Lalith Athulathmudali however denied the Sri Lankna navy's involvement.
Thirty-three years on the perpetrators have not faced justice.