According to this: 10 Largest Overwater Villas in Maldives - linaratravel, Gili Lankanfushi is larger. However, staff at the St. Regis are adamant that the John Jacob is larger, even when I mentioned Gili. Maybe it's the way it's configured/different ways of counting the square footage?

Of course, if it's larger than the Private reserve, than at least according to that article, it'd likely be the largest in the world. When I suggested this to staff though, they were resistant to the notion. I don't know what else out there would be larger.... any guesses?