Neil79, I don't think it is a bad image, it is just that you can only do so much to the contrast / saturation levels before it begins to look odd.
Constructive criticism wise.....
I think the biggest problem with the picture is the sky. It was obviously a nice day when you took the shot. The sky is blue but there doesn't appear to be any clouds. You can see that near the horizon there is a greyish/blue haze and that is about it.
I think had the picture had some nice fluffy white clouds in it, then it would have been a different proposition.
There are also two conflicting points of interest, the big blob of sand/seaweed and the Church/Castle ruins. Is the picture a crop? Can you crop out the blob in bottom middle, add in some more sky above the ruins and perhaps line the ruins up on a 'rule of thirds' intersection? The picture may have more impact as a result.
As others have already mentioned there are a few things you can do.
1) Invest in a polarising filter to boost the blue of the sky, you can also alter the reflective nature of water with one too.
2) Graduated Grey filter. One of the bugbears of Landscare photography is the fact that skies can often be too bright, its a balancing act between exposing for the detail in the ground or exposing for the detail in the sky. Graduated filters can help immensely.
3) I don't know if your budge allows for it, but Lightroom 3. An amazing program which can do an awful lot to improve photographs. The sharpening / noise reduction abilities are amazing.
One last thing. Take a look at a couple of Flickr groups which have some really nice Landscape shots. I am sure they will inspire you. Stick at it, the recent shots in Black and White you have posted in another thread are really good.
The British Countryside
Sky and Clouds
Landscape