The five men from London died in the sea at the East Sussex resort of Camber Sands in August.
The East Sussex coroner said Mohit Dupar died in July, getting into difficulty on the same day that 19-year-old Gustavo Silva Da Cruz died.
Mr Dupar died in hospital four days later but details of his death have only now been publicly revealed.
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Among the five friends who died were Kenugen Saththiyanathan, 18, known as Ken, and his brother Kobikanthan Saththiyanathan, 22, known as Kobi, both of Normandy Way, Erith, south-east London.
Nitharsan Ravi, 22, of Admaston Road, Plumstead, south-east London, Inthushan Sriskantharasa, 23, of Chadwell Road, Grays, Essex, and Gurushanth Srithavarajah, 27, of Elsa Road, Welling, south-east London, were also among the group.
Pre-inquest reviews into their deaths will be held in Hastings on Tuesday following full inquests into how Brazilian national Mr Silva Da Cruz and Mr Dupar, of Cranmer Road, Hayes, west London, who was believed to be in his 30s, died.
A beach where five friends died during a day trip claimed a seventh life in the summer, a coroner has disclosed.