What is meant by "while you were looking on" (tanẓurūn)?

Imām Ibn al-Jawzī (d. 597/1201) summarized the scholars' opinions in his book "Zād al-Masīr" as follows:

1. It means that they saw this with their eyes, meaning: "while you watched them drowning." .
2. It means awareness or knowledge (in this interpretation, the meaning is: "while you know this"), as in verses which say "Have you not seen" with the meaning of "considered". [al-Farrāʾ]