Very interesting image, it certainly has potential.
I agree with Stephen (NVSeal) about the clouds and shore. I'd like to add that one thing is very good about the shore; the overhanging grasses
It's one advantage that these grassmodels give this nice coverage themselves without having to fiddle that much to make something look like this.
Nonetheless you've made good use of it and it looks really really good!
There's one other thing I'd certainly change and that's the size of and roughness of the waves. I'd make it much less rough and also quite much smaller wavescale.
The transparency color is well chosen I think, so I'd stick to that.
Maybe adding one or two extra tree-populations would give that extra variation and natural look.
You could then also render it a tad smaller with higher AA settings to give the trees a smoother look.
Adding a fill light opposite to your main light and with 10-15% of the main light's strength would fill the shadows nicely.
Especially in the middle of the image the shadows of the trees miss definition and the grasses are not or barely visible.
Filling the shadows with a fill light or increasing the GI strength (environment light settings) will improve this.
Like many are used from me quite some suggestion, but I'd like to pronounce/rephrase this is good work with potential, so I hope you'll post an update.
Martin
