The midget submarines were lifted from the harbour and taken to Clark Island within days of the attack. Ha-21 was badly battered — it had possibly collided with the seabed at least once and subjected to repeated depth charges.
The bodies of all the crew members were removed from the vessels. Lieutenant Keiu Matsuo and Petty Officer First Class Masao Tsuzuku, in Ha-21, were found to have bullet wounds to the head and are believed to have committed suicide.
A civilian torpedo fitter, Frank Lingard, based at Garden Island, who disarmed the torpedo which had ran aground at Garden Island, also disarmed the depth charges and torpedoes from both midget submarines.
Intelligence was gathered from both submarines. Lieutenant Matsuo’s submarine contained British Admiralty charts with rendezvous points. There were also photographs of various areas and targets in and around Sydney and Newcastle, and aerial photographs of Sydney Harbour.
There were also personal items including a a ceremonial sword given to Lieutenant Matsuo by his father, his service pistol, a camera and several embroidered scarves. A puzzle box was also found on one of the submarines. Robert Judge, a civilian boilermaker, who cut the midget submarines open found the box and retained it as a keepsake. These personal items are now on display at the Australian War Memorial, Canberra.