This story was told by Scheherazade on the 940th to 946th nights.
A poor fisherman named Abdullah had a large family, but over a period of days, he was unable to catch any fish. After being encouraged by his wife, he cast his net once more. This time he pulls in a merman, also named Abdullah, and they became partners. Abdullah of the Land traded fruit, and Abdullah of the Sea traded precious jewels. Soon the fisherman began to prosper. However, it happened one day that a sheikh investigating the theft of the Queen's jewelry saw the humble fisherman pawning extravagant gems, and arrested him. Fortunately, the Queen recognized immediately that these were not her jewels. In apology, the King bought all of Abdullah's gems and gave him the hand of the Princess in marriage. As the king's son-in-law, Abdullah became wealthy and respected.
He continued trading with Abdullah the merman. They discussed the pilgrimage to Mecca and Abdullah of the Land decided to make the journey and, as Abdullah of the Sea could not make the trip, would take along a gift for him. Abdullah of the Sea invites him underwater to his home for a feast, and gives him ointment that allows him to breathe water. Under the sea, Abdullah of the Land sees many marvelous things. The food is all raw fish, people wear no clothes, and they celebrate at funerals. However, this last one disturbs the fisherman, who explains that humans mourn at funerals. The affronted merman cast him out, saying that he cannot trust someone who will not rejoice in returning a gift to Allah. Their partnership ends. Abdullah of the Land continues to prosper, but sadly never sees the merman again.