[draygin]

It's a good start. I've circled your biggest issues and will give suggestions for minor ones.

With that said we'll start at the beginning

1.) The water to wall transition is very bad. You need some kind of actual tiling that makes the transition. If you look at the predefined tiles you'll see some good water to cliff tiles you can try using and they'll show you the best way to start using them.

2.) The way your walls switch back and forth in two different styles looks ackward and clumsy. You use the predefined cave walls in one way then on the next well you use what you're using as the background of your cave level. I suggest trying to make the walls all uniform in style.

3.) Where the wall to the water joines the wall on the right looks ackward as well. I would suggest removing those three blocks and finding some way to make it so that your up and down wall joinst he wall going left to right. Right now it's going straight up and over it and it throws the 3 dimensional view off.

Your bridge is very well done and you should be pleased with that.

Something to consider for future levels is to make your levels less square and uniform. It will give them a more natural look and in the long run you'll be a better level maker for it.

I'll post some screen shots later with various ways you can do the the cave walls that look fairly nice. Always remember when tiling that a tile is what you can make of it and not always what it was originally intended to be. (Like your bridge.)