The Florian Triangle (literally translated as Zone of Demonic Triangle) is a stretch of sea that one has to cross over when heading from Water 7 to Fish-Man Island. It is covered in a fog so thick that it blocks out all sunlight.
According to Kokoro, many pirate and commercial ships mysteriously went missing every year and, sometimes, a ship will be found sailing without any people onboard. It has also been said that there are many haunted ships with dead bodies sailing across the sea though it is revealed that all this is attributed to Brook.
While some of these disappearances are due to Moria's scheme, ships in the area vanished even before the arrival of Moria's ship, Thriller Bark, ten years before the series. This mystery is confirmed by an unknown ominous entity larger than Thriller Bark. It was barely seen by Lola through the fog. It is so large that it completely dwarfs Thriller Bark, the world's largest pirate ship, in sheer size, possibly making it the biggest creature to appear in the series thus far.
The Florian Triangle is based on a legend about the Bermuda Triangle with its purported mysterious disappearances of ships and aircrafts.
The mysterious entities living in the Florian Triangle greatly resemble traditional depictions of Umibozu, enormous sea monsters said to be the form of priests who died at sea.
Funny enough, when the Straw Hat Pirates first heard of the Florian Triangle, some of them made a casual prediction on what they thought they might encounter, with all of them coming true.:
Luffy thought he might encounter a living skeleton, which they did, in the form of Brook.