And I should say that I really like the current look. :D I think the variance of width looks good here.

But if you want to do a constant width path, why not use a wide smooth path from the start? You can apply fills and sheet effects to that like to a polygon.

If you want to keep one side of the polygon you've already drawn, use the Break command (BREAK) to remove the other side, then change the width and perhaps move it a bit.

The problem seem to the brightness of the Texturize effect, which you've set to 100%. That removes all the shadow. Try setting it to 80% or something like that.

That looks a bit like an installation with insufficient rights (non-admin). Are you running CC3+ on a Windows account with reduced rights?

As a first thing, I'd try to run the latest update for CC3+ (update 28) . Download it from your registration page, right-click the file and choose "Run as Administrator" to execute it. Does that help?

If not, I would recommend a reinstall, making sure you also run the setup for CC3+ by right-clicking the file and choosing "Run as administrator" to execute it.

The water level in FT3+ is world-wide. High altitude lakes or below sea-level land is not something FT does, sorry.

EDIT: This was wrong, see jslayton's answer below.