depth charge fuses to , and when Sea Mist passed over where the submarine had just submerged and dropped a depth charge, she had only five seconds to clear the area. The blast damaged M-21, which inverted and rose to the surface before sinking again. Sea Mist dropped a second depth charge, which damaged one of her two engines in the process and prevented her from making further attacks. Steady Hour and Yarroma continued the attack, dropping seventeen depth charges on believed visual sightings and instrument contacts of the midget over the next three and a half hours. At some point during the night, the crew of M-21 killed themselves. At 04:40, HMAS Canberra recorded that the Japanese may have fired torpedoes at her. This may have been one of many false alarms throughout the night. However, M-21 had attempted to fire its two torpedoes, but failed because of damage to the bow either from HMAS Yandras ramming or depth charges, or a possible collision with USS Chicago, making it possible that M-21 attempted to attack the cruiser. The observer aboard Canberra may have seen bubbles from the compressed air released to fire the torpedoes. Secondary missions As per the operation plan, the five mother submarines waited off Port Hacking on the nights of 1 and 2 June for the midget submarines to return. FRUMEL picked up wireless traffic between the five submarines, leading the Royal Australian Air Force to task three Lockheed Hudsons and two Bristol Beauforts with finding the source of the communications. They were unsuccessful. On 3 June, Sasaki abandoned hope of recovering the midget submarines, and the submarines dispersed on their secondary missions. Attacks on Allied merchant shipping Four of the submarines began operations against Allied merchant shipping. I-21 patrolled north of Sydney, while I-24 patrolled south of Sydney. I-27 began searching off Gabo Island for ships departing Melbourne, and I-29 travelled to Brisbane. I-22 left the group to conduct reconnaissance operations, first at Wellington and Auckland in New Zealand, and then at Suva in Fiji. Between 1 and 25 June, when the four submarines arrived at Kwajalein Atoll in the Marshall Islands to re-supply before proceeding to Japanese shipyards for maintenance, the four submarines attacked at least seven Allied merchant vessels. Three of these were sunk: Iron Chieftain by I-24 on 3 June, Iron Crown by I-27 on 4 June, and Guatemala by I-21 on