Here are some possible additional causes and effects based on the passage:
CAUSE EFFECT
1.) The sun was in Pia’s eyes
- Pia blinked
- Pia saw a silver fish-tail briefly
2. Pia wasn't sure what she saw initially
1. Pia didn't move
- Pia was curious
- Pia wanted to see what/who was there
2. Pia met Lia
3.) Pia wore necklace
- Pia was able to breathe underwater
- Pia was able to explore the coral reef with Lia
2. Pia had an amazing underwater adventure