67. And when harm touches you upon the sea, those that you call upon vanish from you except Him. But when He brings you safe to land, you turn away. And man is ever ungrateful.

When Harm befalls Them, the Disbelievers do not remember anyone except Allah

Allah tells us that when harm befalls people, they call on Him, turning to Him and sincerely beseeching Him. Hence Allah says:

And when harm touches you upon the sea, those that you call upon vanish from you except Him.

meaning, everything they worship besides Allah disappears from their hearts and minds. Similar happened to 'Ikrimah bin Abi Jahl when he fled from the Messenger of Allah after the conquest of Makkah, and headed for Ethiopia. He set out across the sea to go to Ethiopia, but a stormy wind arose. The people said to one another: "None can save you except Allah Alone." 'Ikrimah said to himself, "By Allah if none can benefit on the sea except Allah then no doubt none can benefit on land except Allah. 'O Allah! I promise You that if You bring me safely out of this, I will go and put my hand in the hand of Muhammad and surely, I will find him full of pity, kindness and mercy.'" They came out of it safely and were delivered from the sea. Then 'Ikrimah went to the Messenger of Allah, and declared his Islam, and he became a good Muslim, may Allah be pleased with him.

But when He brings you safe to land, you turn away.

means, you forget what you remembered of Divine Oneness (Tawhid) when you were on the sea, and you turn away from calling on Him Alone with no partner or associate.

And man is ever ungrateful. means, by nature he forgets and denies His blessings, except for those whom Allah protects.