- increase your exposure (use the Exposure Compensation feature to brighten what your camera is choosing if necessary).
- ditch the UV filter. 90% likelihood it is doing nothing but hurting the quality of your photos (the remaining 10% is if you bought a very high-quality filter, in which case it isn't hurting but also not really helping).
- purchase a good quality circular polarizer.
- get a lens hood for the lens (flare is not apparent in the samples, but a hood is cheap and easy protection from flares and haze).
- shoot in RAW if you are comfortable doing post-procesing in Lightroom or equivalent.
A good quality circular polarizer makes the skies "more blue" by reducing light which is reflected off whispy clouds in the atmosphere (leaving the more-likely-to-not-be-polarized scattered blue wavelengths (reflected light will generally be undulating left-right; the polarizer only lets light through which is undulating top-bottom, so you reduce a significant amount of haze). The effect is even more dramatic on water, which can go from very blah due to surface reflections to a nice relaxing blue-green, although in your samples I'm seeing much less water reflections than whispy cloud reflections. I say "good quality" because, while polarization isn't a dark science, allowing as much light through (and thus keeping a nice bright exposure) while keeping flares and such off the finished product.
On that particular lens, the front element does not rotate with auto-focus (which makes using a circular polarizer much easier). However, if you zoom in or out, there is a very slight front-element rotation. So, if you get the skies a perfect azure zoomed in, then zoom out for a more panoramic shot, expect to need to twist that polarizing filter just a little bit to get it back to the same orientation as you had had it before.
UV filters are not necessary for digital cameras. They were moderately useful for film as film is sensitive to UV light and so you could end up with "not what you saw" on the film without a UV filter at times. But not so with digital. It is primarily just a quick checkout throw-in that camera stores make a killing off of.
The hood for that lens is fairly expensive, but there is nothing magical about the Canon brand name on it. I just bought one from Altura for about a third what Canon was asking (the same kit lens).
A lot of subtle corrections can be made in post-processing to make those blues really "pop". As a warning, though, if they are dull and drab out of camera, any post-processing is just going to make them fake looking. Don't use post-processing to rescue or edit; use it to enhance what you captured in-camera.