No, this isn't about global warming and rising oceans. Homeowners are underwater on their mortgages.

About 21.8 percent of all owners were underwater as of March 31, the Seattle-based real estate data service said in a report today. At the end of the fourth quarter, 17.6 percent of homeowners owed more than their original mortgage, while 14.3 percent had negative equity three months earlier.

It's amazing to see 50% more home mortgages go underwater in just 6 months!

Property values dropped 14 percent from a year earlier in the first quarter, reducing the median value of U.S. single- family homes, condominiums and cooperatives to $182,378, Zillow said. The decline has left about 20.4 million of the U.S.’s 93 million houses, condos and co-ops with loans higher than the properties are worth.