Almost immediately the stern slipped beneath the English Channel.
Captain James Gerald Stokely Doorly wrote a dramatic account of the vessel's final moments in a report to his employers, the Union Steam Ship Company, saying that the wireless operator barely had time to send an SOS "when the sea smashed along and hissed like a boa up to the after part of the boat deck".
Doorly struggled to the bridge, blew the "abandon ship" signal on a whistle and told the engine room to stop before grabbing a canvas bag containing secret wartime papers, codes and instructions and tossing it over the rail.
Discarding his heavy coat and boots, he pulled on a life belt and slid down a rope into the freezing waters.
His watch stopped at 58 minutes after midnight on 19 November 1917 - just six minutes after the blast which had crippled his ship. He swam to Aparima's row boat, which was packed with survivors and in danger, too, of sinking.
In the darkness they found a life boat, transferred the frightened sailors and watched Aparima disappear. "An eerie moaning rumbled from the boiler room as it became submerged," Doorly reported.
The captain was lucky. Accounts say that of the 110 onboard, 56 were lost, 24 of them New Zealanders. Besides the Kiwis, the crew included seamen from Britain, Australia and India. The Indian sailors were known as "Lascars" and served on British vessels under agreements which gave ship-owners broad control over their employment.
But at least they were paid. The New Zealand cadets were not so fortunate, as Philip Lascelles, who wrote a master's history thesis at Massey University about New Zealanders in the wartime Mercantile Marine, discovered. He has written that "the cadets received no pay, yet they willingly ran the same risks" as officers and seamen.
Parents or guardians of the young men actually paid the Union company for their service, and the Aparima served as an officer cadet training ship with as many as 50 cadets on any voyage.
A year before the ship's final voyage, the company had written to the families of cadets in the light of increased dangers its vessels faced given Germany's decision to wage unrestricted warfare against merchant shipping using its deadly U-boats. The company offered parents the option to remove their boys from ships sailing in dangerous waters.
According to Lascelles, few parents chose that course, often because they did not want to be seen as shirkers, letting their country down.
The Aparima tragedy hit the cadets' families hard, given that they had scrimped and saved to send their boys to sea, often in the hope they would be repaid once their sons completed their training and entered the merchant navy. Dependants of seamen who died as a result of enemy hostilities could claim compensation from the Government. The deal did not extend to the cadets.
In one account Lascelles found, Mary Proudfoot of Queenstown, a widow whose 16-year-old son John was a casualty of the sinking, wrote: "This boy whom I have lost was an only child and I was expecting his assistance to help me in my old age." Mrs Proudfoot added that John's death had "unnerved me - the awfulness of it is too dreadful."
Eventually the Union company made a payout to the families of the drowned cadets, who were eligible for the British War Medal and Mercantile Marine Medal.
The names of 13 New Zealand cadets lost in the disaster are recorded on the Tower Hill Memorial in London. The name of Cadet William Harry Williams, whose mother was the postmistress at Clevedon in South Auckland, is inscribed on the Clevedon war memorial.
And as for the Aparima, she lies on the sea floor, a few kilometres off the English coast. The ship's 4.7-inch gun, mooring cable and anchor are visible to divers who explore the wartime wreck.
