Luqman 31:32
"Mawj ka-l-ẓulal" — a wave "like canopies." "Ẓulal" in Arabic is a sun-shade, a tall covered structure (a roofed seat, a shaded courtyard); the verse describes the wave not horizontally but as a **vertical** shadow — closing in from above, cutting off the light.
وَإِذَا غَشِيَهُم مَّوْجٌ كَٱلظُّلَلِ دَعَوُا۟ ٱللَّهَ مُخْلِصِينَ لَهُ ٱلدِّينَ فَلَمَّا نَجَّىٰهُمْ إِلَى ٱلْبَرِّ فَمِنْهُم مُّقْتَصِدٌ ۚ وَمَا يَجْحَدُ بِـَٔايَـٰتِنَآ إِلَّا كُلُّ خَتَّارٍ كَفُورٍ
When waves, like canopies, cover them, they call upon God, devoting their religion to Him. But when He has delivered them to dry land, some of them waver. No one renounces Our revelations except the treacherous blasphemer
Luqman 31:32 · Translation: talal-itani
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"Muqtaṣid" — the one in the middle, neither fully refusing nor fully accepting; after the distress some swerve into outright denial, some into full faith, and some remain in the middle. The verse is a more specific continuation of 10:22: prayer + rescue + the aftermath.
Observation
High sea waves (8–12 metres) viewed from a ship's deck do form a "shadowing" appearance — especially when the wave surface stands perpendicular to the wind; in marine hydrography this is the well-known "rogue wave" phenomenon. The verse's "ka-l-ẓulal" (like canopies) renders this visual fact in the language of observation; not a metaphor, but a real testimony of seafaring tradition.
Exegesis
Al-Bayḍāwī (Anwār al-Tanzīl) holds that the word "muqtaṣid" sums up three types of human behaviour in the passage from distress to ease. Al-Rāzī suggests reading this verse together with 10:22 — the two are two angles of the same scene.
Sources
Tafsīr: al-Bayḍāwī · Anwār al-Tanzīl; al-Rāzī · Mafātīḥ al-Ghayb. Science: marine hydrography (the visual aspect of high waves, rogue waves).