Interesting documents from Platonov's book (the translation is mine).
Instructions to establish the facts of sinking of enemy ships
Approved by People's Commissar of Navy of USSR admiral Kuznetsov, June 1943
To establish the following evidences confirmed the fact of sinking of enemy warships:
I. For submarines
1. Evidences of sounds of explosions of launched torpedos according to the calculated time to reach the target, distance of torpedo firing, amount of torpedos in salvo (probability of hit), size and parameters of target move; with confirmation of the loss of enemy ship by recon and agential data.
2. Visual observation of fact of sinking the enemy ship by submarine commander after salvo from surface position as well as from underwater position, with indication of observation time and characteristic of actions of enemy ship.
3. Reconnaissance and agential data, confirmed the fact of sinking of enemy ship.
II. For naval aviation
1. For single torpedo-bombers and bombers - observation the fact of sinking the enemy ship by all crewmembers.
2. For attack aircraft and other aircraft - observation the fact of sinking the enemy ship by leading or supporting aircraft.
3. Fotos, confirmed the report of crew about sinking of enemy ship.
4. Reconnaissance and agential data, confirmed the report abou the fact of sinking of enemy ship.
5. The reports of warships or submarines in corresponding area observed the sinking of enemy ship.
III. For MTBs
1. Visual observation the sinking of enemy ship by crewmembers of MTB.
2. Visual observations the sinking of enemy shipo by crewmembers of other MTBs (aircraft), participated in combat run together with MTB which attacked the enemy ship.
3. Reconnaissance and agential data, confirmed the reports about fact of sinking of enemy ship.
IV. For submarine chasers during the sinking of enemy submarine
1. Visual observation of commander of submarine chaser of underwater explosion took place immediately after explosion of depth charge, and surfacing the wrecks of enemy submarine and dead bodies of her crewmembers
2. Reconnaissance and agential data, confirmed the reports about fact of sinking of enemy submarine
Head of Air Forces
colonel-general of aviation
Acting Head of the Naval Department of Political Training
captain 1st rank Kuznetsov
Acting Head of the Naval Department of Combat Training
rear admiral Shelting
Abstract from the order no. 00260 from 20th December 1944 about the control of combat action of Red Banner Baltic Navy
My note about the last case: the captain of Shch-307 commander Nikolai Momot (four torpedo attacks, one successful; reported about two unsuccessful attacks from those four) who avoided the torpedos of "Iku-Turso" 27.10.1942 by skillful manoeuvring wasn't the captain of Shch-307 since 24.02.1944. New captain, lieutenant commander Mikhail Kalinin performed six torpedo attacks on Shch-307 between 10.1944-01.1945, five were unsuccessful but he reported about possible success in all cases according to sound and/or periscope control. The case with three "sinking" transports took place 16.10.1944 when 4 torpedos were launched from 18 cables (the first attack of Kalinin on Shch-307), recon confirmation flight wasn't made after this as well as Soviet naval divers found no any ship wrecks there after the war.5. Brigade of submarines made a significant job since the possibility to enter the sea using skerries arised. But a number of significant disadvantages in combat action was found also.
a) one month delay in deployment of submarines to the ports of Finland caused problems in organization of their combat actions as well as in continuity of their combat control.
b) there is no any cooperation between submarines and aviation up to now. Submarines received the data from reconnaissance flights about enemy transports in 10-18 hours only.
Manoeuvring and group use of submarines is not organized because of this reasons.
c) the results of torpedo attacks are not checked, and this causes false representations about the efficiency of their use. The most unthinkable example is the report case of Shch-307 (home port Turku) which sank three anchored transports in Windau using four-torpedo salvo and this so-called fact wasn't checked by air recon as well as no other confirmations were presented.