Effect? It just looks like a well-executed, natural-looking photo shot with a good wide angle lens to me. Indeed it's very nice.
At one time I might have said they did noise reduction and maybe some HDR work, but with modern gear and great converters like Camera Raw (especiually considering the current set of adjustment abilities), it's not inconceivable to get an image like that right out of a raw file. Landscapes often benefit from increased color saturation, and I can imagine the Clarity control might have helped make the air just seem very clear. It's possible they cloned- (or spot-healed-) out any little bits of debris visible to give the image a very clean feel.
It's also sharpened nicely for web presenetation. There's even a lot of detail in the 2048 pixel version, though at that size you start to see sharpening halos.
Clear, wide angle landscapes with light reflections, not to mention pretty clouds and all the colors of the spectrum, can be very nice indeed, as this shot underscores.
Agree with the last two posts, doubt if there was any post processing involved, however, they image maker did a great job with in-camera exposure, with the details in both highlights and especially the shadows - even though they could be adjusted in post, it always better to get exposure right from the get-go. Also the composition and angle is great, and the absence of lens flare shows the picture was well composed and thought out - the essentials for a really good image.
But one post technique could be applied here and that would be to apply a slight graduated filter to drop the highlight values and give a littel more punch to the clouds - but why bother this is a great image
Very well done in the taking. I might use a couple of ACR tricks to see what happens. Might lighten up the shadowed area to bring out the boat reflection a bit.