try again with an actual calculation of the difference between ocean volume and fresh water volume

[link to water.usgs.gov (secure)]

even if you threw all the ice into the oceans right now it wouldn't raise it any visible amount

based on the approx. percentage of ice

for one cup or 250mL of water

250 x 0.0175 = 4.375

it's 4.375mL of ice

not a bunch of cubes like that

a 250 and 255 in 2 separate cups are indistinguishable in visible volume