Retired Treasure Hunter's Memory

Hmm... Where is this place?
I think I've been there when I was younger.
Ah, that's right, this is the area near Oquilla's Eye!
I couldn't find any treasure near the island so I sailed out until, to my surprise,
I found the most fascinating ruins.
The waters were too deep for me to search down there thoroughly
but from what I saw the ruins were covered in expensive-looking antiquities.
What were these antiquities exactly, you ask? Hahaha, well that's my little secret.

Are you doubting me? I'm sure that map points to the area around Oquilla's Eye.
Are you saying my memory can't be trusted?

It's my first time seeing such a shiny chest.
My poor heart might just burst!
I wonder if there are even more of these treasure chests somewhere out there...