ر ھ وr-h-w
(ن) رَهَا يَرْهُوْ رَهْوًاrahā yarhū rahwan: to be still and calm; also to be wide and open.
رَهْوٌrahw (verbal noun, maṣdar, as a circumstantial accusative, ḥāl): calm, open — the exegetes mention both senses here: leave the sea still, or leave it open. Only once in the Quran: ﴿وَاتْرُكِ الْبَحْرَ رَهْوًا﴾ (Ad-Dukhān 44:24)