The Sea Level Research Group at the University of Colorado has been adding 0.3 millimeters per year to it's sea level measurements. Steve Nerem, the director of the research center, told Fox News that they do this because land masses are also rising, an apparent rebound from the last ice age.
"We have to account for the fact that the ocean basins are actually getting slightly bigger... water volume is expanding," he said, a phenomenon they call glacial isostatic adjustment (GIA).
Nerem indicated in emails to Fox that he believes that sea level and amount of water in the ocean are the same thing, regardless of whether the coast is also rising.