"Slimeline" was the nickname that was given to the first generation of clear sinking lines that came out. They had a sink rate of around 2" per second, had a monofilament core, and the clear coating felt slimy when wet...therefore the nickname. These lines had the problem of lots of line memory due to the mono core, which meant lots and lots of tight little coils and having to stretch them out like crazy prior to every use to get rid of most of them.
The newest generation of clear sinking lines are great. They have low memory, some specifically designed for use in our colder water climate. They come in different lengths and tapers to suit distance casting or regular fishing. Some, like the Cortland Clear Camo, sink closer to the true intermediate sink rate of 1" per second, while most are actually closer to the sink rate of a Type II line.
There are a few clear floating lines out there, I think one of them put out by the smaller company Monic. It's been a while since I've shopped for gear, so I'm not 100% sure. I've only heard of one guy using a clear floater, and that was for really spooky fish in small spring creeks in the US. For our type of fishing up here, I don't think it's necessary...but we all go with what we're comfortable with. I wouldn't like it because I wouldn't be able to see what my line or line tip are doing...sometimes strikes are so light all you see is the tip slightly moving.