Marisabel‘s (Diving Bel‘s) earrings are unique and cursed items. They are Cursed with the Mermaid’s Curse. When she was 12, all the kids her age went diving often. They used to dive for toy treasure in the summer. Her dad colored the treasure and put it into the relatively shallow water. The kids then went diving for them as training.
One day she found the earrings while diving. She told her dad about them, but only her and Nura know that they are cursed and allow her to talk to Merfolk. In the Tales from the Sea of Thieves book, Diving Bel talks to Merfolk at one point.