The correct past tense of the verb ‘sink’ is ‘sank’. ‘Sunk’ is actually the past participle form of the verb. To clarify further:
- Present Tense: sink
- Past Tense: sank
- Past Participle: sunk
For example, you could say ‘Yesterday, I sank the ball into the water.’ In this sentence, ‘sank’ correctly indicates that the action happened in the past. If you were to use ‘sunk’, it would be in a different context, such as ‘The ship has sunk.’ Here, ‘sunk’ is used to indicate the completed action, but it’s not functioning as the past tense in a simple sentence.