The tragedy struck the cadets when they had gone to the river for a bath, police said.
The victims were part of the over 1000 NCC cadets from across the country who have congregated at Malayattoor, a hilly area, for the 8-day camp which began on December 23.
The camp was being organised by the Ernakulam NCC Group of Kerala NCC Directorate.
Defence Minister A K Antony expressed his anguish at the tragedy.
