What event did Arethusa witness while fleeing underwater?

Arethusa, in Greek mythology, is often associated with a story involving her flight from the river god Alpheus. In her escape, she metamorphoses into a spring of water and travels underwater. The event she is said to witness during this flight is the abduction of Persephone by Hades.

This event is significant in mythology as it marks a pivotal moment in the myth of Persephone, who is taken to the Underworld, leading to the eventual changing of seasons. Persephone's abduction is a key theme that intertwines with various aspects of Greek mythology, particularly with the agricultural cycles and the relationship between Demeter (Persephone's mother) and Hades. Arethusa’s experience of witnessing this moment enriches the narrative of her own escape and highlights how interconnected the stories of different figures are in Greek myths.