The commanding officer of Britain's Special Boat Service commandos has died after a training accident in Norway.
The Ministry of Defence said a board of inquiry would investigate the death of Lt Col Richard van der Horst.
In line with standard policy relating to the special forces, the Ministry of Defence would only describe Lt Col van der Horst as a Royal Marines officer.
Similar in status to the better-known Special Air Service, the SBS's most famous veteran is Lord Ashdown.
Lt Col van der Horst was in his 30s and had been made an OBE for his service during the Iraq war.
A spokesman said the MoD had conveyed its deepest sympathies to his family.
Members of the Royal Marines are chosen to join the elite band of SBS members only after a gruelling physical and mental selection process.
The focus of their operations tends to be from the sea but they also operate inland, and served in both Afghanistan and Iraq.