A federal trial began for a married couple accused of orchestrating a $300 million fraud involving thousands of investors who were promised big profits by purchasing dilapidated properties in the Florida Keys and elsewhere that would be transformed into luxurious resorts.

Instead, prosecutors say Fred Davis “Dave” Clark Jr., former president of now-defunct Cay Clubs Resorts and Marinas, and Cristal Clark, a top sales agent, defrauded banks and about 1,400 individual investors through a series of misleading marketing materials and false statements. The investors in some cases were promised quick returns of 15 to 20 percent, according to court documents.