Just to provide another data point: I negotiated an upgrade rate of $194++/night to go from a water villa to a retreat water villa for 21 nights during the Dec 2019 - Jan 2020 festive season. I used the low figure for 2019 upgrade rates in the sticky as a reference point in my negotiations. Not sure if it helped but it is our third visit to Rangali and we are both diamonds.

Reservations on Hilton’s website all say Retreat Water Villa. Looking forward to snorkeling right off our villa and swimming to the drop off / house reef.