إِنَّ فِى ذَٰلِكَ لَءَايَٰتٍ وَإِن كُنَّا لَمُبْتَلِينَ
The word order must be recorded: āyāt is plural. In the Qurʾān this pattern most often comes in the singular (inna fī dhālika la-āyatan). Here it comes in the plural.
I record this as an observation: the narrative told is not a single event — the call, the objection, the ship, the deliverance, the drowning. The plural fits the number of steps in the narrative.
The lexicographers dwell on the word order: in here is the lightened form of the heavy inna (mukhaffafa mina'l-thaqīla), and the lām is the distinguishing lām that marks it off. The sentence, that is, is not a negation but an emphatic assertion: "We were surely putting to the test."
The root ب-ل-و / ب-ل-ي: to try, to test; and to wear out, to wear down. Ibtilāʾ — testing. The root was treated at al-Mulk 67/2 (li-yabluwakum ayyukum aḥsanu ʿamalā) and at al-ʿAnkabūt 29/2-3. I do not repeat it here.
And the place of the sentence must be recorded: at the close of the narrative comes the word testing. What is told, that is, is sealed not as a report of destruction but as an instance of a testing.
I give this as my own reading, its ground being this position of the sentence. And the same frame was treated at al-Furqān 25/20 (wa jaʿalnā baʿḍakum li-baʿḍin fitnatan a-taṣbirūn) — where it was recorded that the testing comes by the hand of other people. I rely on that treatment.