This is more of an outline and proof of concept than anything else - just the first step in to making the map proper.
As you can see, this is a map of North America. The land itself is unchanged, but sea levels have risen 300 meters. This is a world that has suffered more than a melting of the ice caps: at some point in the past, the Earth passed through a massive cluster of comets. The comets did no physical damage, the cluster being more of an icy cloud, but the result of so much water vapor being released into the atmosphere inundated the world in a great deluge. The process was gradual, though - it took the Earth some time to travel through the cloud - and many civilizations survived by relocating to higher ground. Although reduced to turn-of-the-century technology on the most part, there are still relics of the past hidden in the world.
I chose this sea level because it resulted in a great interior sea, complete with the island of Appalachia and surrounding isles, while still retaining some contours of the old continent. Although the coastline is primarily composed of fjords and skerries, I would assume that sedimentation would, over time, convert much of the rugged coast into marshland, filling in some of the gaps.
Even though the map, in current form, is relatively accurate for such a sea rise, I would still like some input on the design - after all, accuracy isn't everything. Additionally, interior bodies of water have not yet been dealt with (speculation on that is a little trickier, and I'm currently trying to figure out what the general climate and water flow for the region would be), so suggestions for that would be greatly appreciated as well.
As I said before, this is a rough draft - the lines are pixelated and the general workmanship of the map is quite shoddy. There is little originality to the map in its present state, but that will soon be repaired. After making any needed changes and cleaning the map up, I will be adding climate and political divisions next.