Riddle me this batman...

Why do ships far away look like they're sinking under the sea? If Earth was round, It's just a matter of perspective. So then how would a flat Earth explain this?

You can find it explained here in our wiki http://www.theflatearthsociety.org/tiki/tiki-index.php?page=Ships%20appear%20to%20sink%20as%20they%20recede%20past%20the%20horizon