Edit: just got a chance to see the original on my own calibrated monitor rather than the crappy one I originally saw it and photoshoped the copies with... actually the image is reasonably good colour and contrast wise, I still would have done what I did but much more subtly for printing.
But for online displays I would have pushed it to something just short of the edit I included.
First off... you've got some nice shots in that gallery, good compositions, good subjects, thanks for sharing
how I see it is ....
1st I'd clone out the rubbish/trash under the chairs (optional)
2nd I'd use curves to pull down the shadows and make them a bit darker (not to black though but darker) pull down midtones a tiny bit as well just to see.
I'd also lift the highlights till the brightest part of the clouds are _ almost _ pure white
honestly this may be all you feel you need to do - this gives it a lot more "pop" - that's up to you.
3rd: I'd adjust the colours make them more vibrant You'll probably find that pulling down shadow brightness would have already made the sea (particularly the background) and the umbrella's colour more intense but you might need more - I'd increase blue and aqua saturation a bit and pull the brightness down a bit for those two colours. The other colours I'd tweak with a bit, but less than the blues.
4th a bit more sharpening, it's a bit soft when viewed at it's largest resolution.
(assuming photoshop) I'd either give it
A: a two pass sharpen (
http://www.creativepro.com/story/feature/12189.html )
or
B: a Highpass effect (duplicate layer, turn new layer's blending to softlight, drop layer opacity to 50%, go to filter, other/highpass, tweak the pixel size until you get some pop, go back adjust opacity % / blending mode to suit) and then a normal sharpen process (on the lower layer not on the highpassed layer).
Here's some quick and dirty efforts on your original (I'll delete this some time in the next week or two, if your not happy about me editing your images I'll take them down if you message me to do so) I've blown the highlights in the sand out a bit much losing detail (this was because I was working on the sky highlights), you may or may not like this but I'd have made a separate adjustment curve for the foreground and not pushed the highlights so high on that one (or used a layer mask to reduce the effect on the foreground)
http://www.pbase.com/marxz/forumstuff
Original:
processed (no cloning)