How? Polar ice caps melting? The earth has a finite amount of water. It is either gas, liquid, or solid. The earth is like a container; you fill it with ice and add enough water to float the ice to the brim. What happens when the ice melts?
Ice in water, sure, but ice on land will melt and run into somewhere else. Still, however, the rise will not be allthat substantial considering how much water is currently in the ocean compared to inland and mountain glaciers.
STOP IT! You’re injecting facts and science when mere emotion is called for.
You should be banished to a museum or something.
Most of the ice in the world is located in Antartica, which is a continent. If the ice melts off Antartica and flows into the ocean then yes, the sea level will rise considerably. However, in order to do that, Antartica would have to be above freezing temperatures, which it isn’t. Any large scale melting of Antartica would take millenia of higher temperatures.
If you're doing this in a "rocks glass" the level stays the same. That's true because the glass is a "container" that defines a specific volume. The earth does not meet the definition of a container as it does not define a specific volume, as the ice melts the resultant additional water just spreads out over a larger and larger area.
This whole "sea-level" thing is really confusing as it largely depends on where you are measuring the surface. The earth is rotating on it's axis causing the water surface to "bulge" outward along the equator because of centrifugal force. So the sea-level is deeper at the equator than it is at the poles. If it weren't for rotation the water's surface would still be acted on by gravity. The force of gravity, if measured at many locations, is a vector force pointing at the Earth's center of mass. Most people would expect that to be "straight down". However, Earth's mass is not evenly distributed. this effect is caused by large/dense masses of asteroid belt material which struck Earth and remain lodged in the crust. Their influence on gravity is to create an anomaly where "straight down" is not at right angles to the surface. The anomalies create "bumps" in the gravity field and therefore dimples in the sea-level. Additionally, shifts in the crust at the bottom of the oceans (landslides, earth quakes, and lateral shifts) will also introduces dynamic changes in measured depth.
To measure "sea-level" requires that all these forces be accounted for which isn't as easy as it seems because the Earth also wobbles as it rotates, causing all of the above noted forces to dance around.
I almost forgot the most significant force acting on our oceans; the Moon interacts with the ocean water to create the tides which can vary by feet! The Moon's orbit is also changing with time and so introduces more variability in determining "sea-level".
Regards,
GtG
PS Measuring "sea-level" is not quite as easy as marching down to the shore with a ruler.
PPS As to "gravity anomalies", there is a rather large one off the Florida coast which lay under the orbital insertion path of the Apollo Moon shots. It required some coordinate changes to keep everything on track. (Bermuda Triangle? You Bet! Not Kidding!)