Overall meaning : The Almighty says: The two bodies of water are not alike. The water of one is sweet, refreshing and pleasant to drink, while that of the other is salty and bitter; but from both you eat fresh flesh and bring forth ornaments, such as pearls and coral, which you wear; and you see the ships ploughing their way through both, so you may seek His bounty and earn your livelihoods, and that you may give thanks to Him.
He causes the night to pass into the day, thereby bringing forth light; and He causes the day to pass into the night, thereby bringing forth darkness, and He has made the sun and the moon subservient to His laws, each moving in an orbit of its own for your own benefit, until an appointed term.
That is Allah, your Lord, to whom belongs all sovereignty: the idols whom you invoke besides Him do not possess anything at all—not even the thin white skin of a date stone!
If you call upon them, they cannot hear your prayer; and even if they did, they would not answer you. On the Day of Resurrection, they will disown your worshipping them besides Allah. None can inform you of the truth, Muhammad, like Allah, the All-Aware.