Thessaloniki was the older sister of Alexander the Great. She was a beautiful girl with long blond hair, the same colour as her brother's. Thessaloniki loved her younger brother Alexander immensely. When he went on expeditions of war, she would shut herself in her room and pray to the gods so that her beloved Alexander will come back to their palace safe and alive. One day as she was praying, Athena saw her and felt sorry seeing the tears running down on the beautiful girl's face. She decided to to leave Olympus and come to the palace to help her but without anybody knowing her true identity. At the palace door she met one of Thessaloniki's women slaves. Athena gave the slave as mall jar of water, and told her that this water, was not like any other water- it was eternal water. Who ever drunk this water, will always stay alive and never die. "Take it to your mistress", said Athena to the slave, "and tell her to give it to her brother Alexander to drink it and he will stay immortal". The slave did as Athena told her and presented the jar with the precious water to Thessaloniki. After being told all about what happened, she was overwhelmed with happiness. Her prayers were finally answered! When her beloved Alexander would come back to the palace, she would give him the eternal water and he would become immortal, living for ever. However, other are the plans of the gods and other are the wishes of mortals. Thessaloniki forgot to put the jar of the eternal water in a safe place and left it on the table. The next day, while she was weaving, she felt thirsty, and ordered one of her slaves to give her some water to drink. The slave was too lazy to go get water from the well and decided to use the water from the jar and take it to Thessaloniki. All the water in the jar filled one full glass."That's enough for her", the slave thought and gave it to her mistress to drink. Feeling very thirsty, Thessaloniki drunk the water down to the last drop without giving it any thought. When she got up and went to the other room and found the jar empty, she realized what had just happened. She went mad, she started wailing and crying, but it was too late, she had drunk the eternal water that would have made her beloved Alexander immortal. In her madness, she run to the sea and fell off a cliff to kill herself. She fell deep into the sea, but she could not die because now she had become immortal. Athena saw her, and felt sorry for her once again, she decided to turn Thessaloniki into a mermaid, and thus from that day on, Alexander's beautiful blond sister was half woman and half fish. However, her mind still remained mad, unable to forgive herself for drinking the eternal water she was saving for Alexander. Since that time, she swims the seas and the oceans, and when she meets a ship, she always asks the captain: "Is Alexander Alive?" If the captain of the ship tells her "Yes, he lives and reigns, and the world he conquers" she feels happy and lets the waters be calm and blue and the ship to pass to safety. However, if she receives a negative answer, she gets angry and makes the sea stormy with her tail, and the ship sinks.
This is the tale of the eternal water and the mermaid as told to me by my grandmother when I was a child. May God bless her soul.