Nikolai Lunin did not directly observe the result of K-21's torpedo attack on the Tirpitz, but noted sounds of explosions which he interpreted as torpedo hits.
Notes on verification
Multiple independent Russian-language sources (Wikipedia articles on both the attack and submarine K-21, plus historian-cited popular history site) and an English-language mirror consistently confirm that Lunin did not visually confirm the torpedo hits and relied on explosion sounds.
Sources
- Attack on the battleship Tirpitz by submarine K-21 (en.wikipedia.org)
- https://military-history.fandom.com/wiki/Attack_on_the_battleship_Tirpitz_by_submarine_K-21 (military-history.fandom.com)
- https://russian7.ru/post/k-21-protiv-tirpica-kak-sovetskaya-pod/ (russian7.ru)