The Flame of Time
“You see, time travel is a lot like sailing. That is why so many of the timestriding vehicles are old ships, because it is appropriate. I did some sailing once, during the time of Red Jon’s reign of terror over the Sea of Wolves. He was a great fat odd fellow. Anyway, the present is like an island in time, the Time Dimension is much like a sea, a great big sea that envelopes all the other planes, like a blanket. When you sail back or forward in time you sail further away from the island, and the waters of time get deeper and darker. That is why travel too far either way is at times impossible and always dangerous. You sail the seas of time, above reality and you can look into the waters and see the world as time unravels below the surface and the Zeitspringer technology or your chrono-magic drops a kind of anchor that will link you back to the world in that era. But if the waters are too deep and you don’t have a hawser long enough to touch reality you can’t go to that time and may be lost in time. There are denizens of the Time sea that can swim the deeper waters, Monsters of Time. I have seen a few…trust me you don’t want to see them.”
-An excerpt by Griff Byron from De Rerum Tempus: Liber Secundus.