Nearly one in three Florida mortgage borrowers owed more on their loans than their homes were worth in the third quarter, according to First American CoreLogic of Santa Ana, Calif. About 1.2-million of Florida's 4.2-million mortgages — 29.2 percent — were upside down. If home prices dip 5 percent, nearly 200,000 more Florida borrowers would slip under water. Despite rising foreclosures and job losses, most homeowners will hunker down and continue to make mortgage payments, said Sam Khater, senior economist at First American CoreLogic. But negative equity destabilizes the market. More than 7.5-million properties nationwide have negative equity. New York had the lowest rate at 7 percent, followed by Hawaii at 8 percent and Pennsylvania at 9 percent.