A special board of inquiry has been formed to determine the cause of the incident, said TLDM.
The KD Pendekar sank on August 25, two nautical miles southeast of Tanjung Penyusop in Kota Tinggi.
All 39 crew members were rescued before the ship was completely submerged, with no injuries reported, the navy said in an earlier statement.
The ship was believed to have hit an unknown underwater object, causing a leak that resulted in “severe flooding”.
The leak was first detected in the ship’s engine room, spreading rapidly despite efforts to control and stabilise the vessel.
According to the New Straits Times, Arman was a specialist deployed to provide a cordon around the wreck of the KD Pendekar, to ensure the security of sensitive equipment.
He is believed to have drowned while installing floats at the site, said the report.
A postmortem will be conducted at Hospital Sultan Ismail in Johor before his burial in Sabah.
All help and support will be given to his family during this difficult time, the navy added.
The KD Pendekar, a fast craft built in Sweden, was commissioned in July 1979, according to Malaysian media.
Malaysia’s defence minister Khaled Nordin said on August 26 that inspections would be carried out on a third of the navy’s fleet.
He also added that the navy has 10 to 15 ships that are more than 40 years old, reported The Star.
Regarding the sinking of the KD Pendekar, the minister said the age of the vessel may not be the cause, as it had collided with an object.