David and Alberta Purpora, St. Armands Key, sold Unit 502 at the Water Club I, 1241 Gulf of Mexico Drive, to Thomas Grusecki and Christina Grant, of Schiller Park, Ill., as joint tenants with rights of survivorship, for $1,925,000. Built in 1996, the 3,400-square-foot unit has three bedrooms and five bathrooms. It last sold for $771,000 in January 1999.