Designed by Australian Ann Maree Willett primarily using hand-blocked wool felt and feathers,
the 54-cm high bluish-color Deep Blue Sea is adorned with 26 gem-quality opals valued at over $890,000.
The Deep Blue Sea, which was inspired by the Australian Great Barrier Reef, was introduced to the world in February 2007 during the Milan Fashion Week.
After participating in several more runway shows, the hat was sent to the Bonham auction house where it was subsequently appraised and valued in the range of $150,000 to $200,000.
Unfortunately, the hat remains unsold to this day.