“The character’s want or desire or pursuit usually focuses and intensifies as the story evolves; it is not a static, unchanging want.” - Tools of Screenwriting
What began as mere curiosity of the world above the sea, evolved into a full-blown infatuation. The little mermaid princess is head-over-heels in love with the prince and is obsessed with finding a way to be with him.

After her encounter with the prince, her only comfort is sitting in the garden and gaze at a marble statue that resembles her prince. One evening, her sisters take her to the palace where the prince lives. Every evening after, she spends in the waters near the palace.
One day, she asks her grandmother if humans didn’t drowned, if they could live forever. Her grandmother said, “they too must die, and their lives are much shorter than our own. We sometimes love to three hundred years, but when we die, we become foam on the surface of the water. We do not have immortal souls. Human beings have souls that live after their bodies have turned to dust. Their souls rise up through the clear, pure air beyond the glittering stars. As we rise out of the water and behold the earth, they rise to unknown and glorious places that we shall never see.”
The little mermaid said that she would give up hundreds of years to have an immortal soul, and asked how she might gain an immortal soul.
Her grandmother said, “unless a human being loved you so much that you were more precious to him than his father or mother. All his thoughts and all his love would have to be fixed upon you, and he would have to take you for his bride. Only then would his soul glide into your body, and you would obtain a share in the happiness of mankind. He would give a soul to you and retain his own as well.”
After this conversation with her grandmother, the little mermaid’s objective is clear: get the prince to love and marry her so she can win an immortal soul.
