The Royal Malaysian Navy's (RMN) hydrography vessel, KD Perantau, sank after springing a leak during refit work at the Boustead Naval Shipyard in Lumut, Perak.
The vessel, which had been used for hydrographic surveying and meteorological and oceanographic observation missions, was undergoing routine refitting work, which was expected to finish by 10 August 2015.
In a statement, the RMN said: "Before it sank, almost all portable equipment such as motor, pump and measuring equipment had been removed from the vessel to enable it to undergo the refit.
"Nonetheless, the RMN will set up a board of inquiry to identify the cause of the incident."
There were no injuries reported during the event and efforts are underway to rescue the vessel.
Built at the Hong Leong-Lursen Shipyard in Penang, KD Perantau entered service in October 1998.
The 67.8m-long, 13.3m-wide hydrographic survey vessel is capable of cruising at a maximum speed of 16k and features the latest navigation and survey systems, including the navigation and command system and hypack acquisition system.
The vessel is also equipped with two survey launches and four multipurpose boats, in addition to three winches, two cranes and a winch for the STN Atlas side-scan sonar.