Wondrous item, uncommon.
This collection of manuscripts in a Prussian blue leather binder describes a myriad of aquatic creatures and plants. A character in possession of this book receives advantage on Intelligence (Investigation) checks when able to reference it to identify and learn more about aquatic monsters, creatures, or plants. If a character spends 48 hours over a period of 6 days studying the book’s contents, the effect becomes permanent and no longer requires referencing the book.