Answer:
The lines suggest that the speaker is watching a girl whose face is lit up as she looks at the treasure she found.
Step-by-step explanation:
The poem talks about how the sea is full of valuable and brilliant treasures, but these rich treasures belong to the sea and not to humans, so it is correct to leave them in the sea.
In this regard, we can see that the speaker is seeing a girl who found a treasure in the sea. It is possible to see her face illuminated by the precious treasure she observes.