A spokesman for the Exeter and Greater Devon District Coroner's office confirmed there would be no inquest into the death of Gareth Jenkins, 25.
Lt Jenkins, from Colwyn Bay, Conwy, collapsed at the Commando Training Centre, Lympstone, Devon, while on a 30-mile (48km) march in May.
The former Eirias High School pupil played for Colwyn Bay Rugby Club.
A Royal Marines trainee who collapsed on a training exercise on Dartmoor died of natural causes.