Its true that a lot of land would be covered by melted ice but even then, over 90% of earth would still be above sea level as shown here: http://www.dailymail.co.uk/sciencetech/article-2488452/Map-r...

Also, fossil evidence doesn't not support a worldwide flood. If a worldwide flood would have happened you have have fossils from that era all over the place in sediments of rock, but you don't. They are all found neatly organized in their own respective layers. Here is some more info if you are interested: http://rationalwiki.org/wiki/Global_flood#Fossil_layers

I think a localized flood is a much better explanation for people who believe that part of the bible.