Japan's defence minister has sacked his navy chief and punished dozens of officials after a series of scandals.
Mr Ishiba pledged firm and prompt action
Shigeru Ishiba acted after an official report criticised the navy over a collision between a destroyer and a fishing vessel.
Two fishermen are missing presumed dead after the destroyer Atago ploughed into a trawler last month.
Other embarrassing incidents included the leaking of data about a radar system and a fire on board a navy ship.
Mr Ishiba dismissed Admiral Eiji Yoshikawa - the country's top admiral - as well as fining and disciplining more than 80 other defence officials.
The report into the incidents was particularly scathing about last month's collision.
The document said four crew members aboard the Atago were missing and a radar had been left unattended when it crashed.
The ship's commander and his deputy had apparently both gone for a nap.
"The watch was not conducted appropriately," Mr Ishiba said.
"We promise to take preventive measures firmly and promptly."
The BBC's Chris Hogg, in Tokyo, says Japan is officially a pacifist country, so any incident involving the military is particularly sensitive.
The scandals have shaken public trust in the naval service, our correspondent adds.