Overall meaning :
Allah, Glorified be He, mentions one of His countless favours which He has so graciously bestowed upon mankind: Do you not see, Muhammad, that the ships sail through the sea, after having made them subservient to His law for people’s benefit, as a favour from Him to them, to show you, people, some of his signs? Surely in this there are clear signs for every steadfast, thankful person.
Then He depicts the condition of some people when they suffer distress and face hardships at sea: When these idolaters are at sea and the waves, like mountains or overshadowing clouds, engulf them and they fear drowning, they sincerely call upon Allah alone; however, after He saves them from drowning and brings them back safe to land, some of them remain mindful of Allah’s favours and give thanks for them but not enough, while others deny them altogether. Only a treacherous and ungrateful person denies Our signs that testify to Our power and oneness.