NASA says the world's seas are rising at uneven rates and even are retreating in some places.
But the space agency says it can't predict how fast seas will rise in the future in part because melting ice sheets aren't well-understood.
NASA appointed a team of researchers last year from a variety of fields to study sea level rise using data collected from outer space and beneath the oceans.
Eric Rignot of the space agency's Jet Propulsion Laboratory in California says melting ice sheets in the future will drive sea level rise, but there isn't much data on it.
"We've never seen an ice sheet collapse in the past. We don't know what it looks like."
Researchers predict sea levels will rise by about 3 feet but say they don't know how long that will take.
And while Florida is especially vulnerable because of its low elevation, in other places the seas are retreating because of variable ocean currents and weather cycles.
