The housing market has recovered sharply from its worst levels following the mortgage crisis. But even five years later, millions of homeowners are still struggling under huge amounts of home debt.

In the following video, Dan Caplinger, The Motley Fool's director of investment planning, looks at recent data from RealtyTrac noting that 9.3 million homeowners remain underwater on their homes by at least 25%. Dan points out how even a big rise in prices and efforts from JPMorgan Chase (NYSE:JPM), Bank of America (NYSE:BAC), and Wells Fargo (NYSE:WFC) to agree to modify customer mortgages haven't made a huge dent in those numbers. Dan notes that big problems exist in hard-hit states like Nevada and Florida, causing potential problems for Hovnanian (NYSE:HOV), PulteGroup (NYSE:PHM), and other homebuilders seeking to recover from the worst of the crisis.