Nearly 20 percent of all residential properties with a mortgage in New Jersey are considered "seriously underwater" financially, according to housing data site RealtyTrac.

Jorge Salcado, ThinkStock

The report, which reflects the first quarter of 2014, counted 241,700 Garden State homes in which the owner owes at least 25 percent more than the estimated market value of the property.

"The properties that are underwater represent 19 percent of all mortgages in the state of New Jersey," said Daren Blomquist, vice president of RealtyTrac.

Nationwide, the underwater situation improved drastically over the past year, from 26 to 17 percent. In New Jersey, meanwhile, the percentage ticked upward.

"I think the reason for that is, New Jersey has not seen as robust a recovery in terms of home prices," Blomquist said. "Compared to some of the other markets, the negative equity problem is a little bit more persistent and stubborn."

On the bright side, close to 230,000 New Jersey properties get the distinction of "equity rich," meaning the owner has at least 50 percent equity.