Hello, Mitchell! We're glad to have you back at the forums!
You have some excellent shots in your collection, I'm assuming that aside from the first shot, they were all done with either your 18-55 or your Sigma 10-20? They're all great pictures, but I'll try to give a bit of constructive criticism to help for the future.
The first shot is nicely composed, but it appears that the focus was wither off, or more probably, there was a bit of motion blur as you shot at 1/13s. To avoid this, try opening up your lens (did you do this with your 18-55 or your 50 1.8?). Of you used your 50mm, don't be afraid to open all the way up to 1.8, and if you used the kit lens, bump up your ISO. Modern DSLRs are designed to surpass ISO 1000, and although your result won't be as clean, it will still be plenty usable. You can even use NR software such as Noise Ninja, a favorite of mine.
Another way to get around blur like this is to simply use a tripod. That would probably be your best bet, but tripods are also heavy to lug around, and can be expensive. If you don't mind carrying one around though, it's a very nice tool to have. Consider a Gorillapod SLR Zoom for a lighter option, or perhaps a small monopod.
As Ian mentioned, your second shot seems a bit busy. I would've gotten a bit closer in, and tried a few different angles (ex: from the wall, from a low angle on the pavement, etc.). Curves and slopes can really improve a photo, so exaggerating or emphasizing the curved wall hay have made it a bit more interesting and appealing. It also seems a bit overexposed and blown out in some areas, so try to avoid that when shooting white objects in broad daylight. Sometimes the noon hours aren't the best for photography as the light is harsh, and it can also make quite harsh shadows.
The third is excellent, the black and white really makes the shot. However, with a flat surface like the ocean in your photo, it's important to make sure that your horizon's flat. You can do this using your camera's virtual horizon, a level built into a tripod or cropping in Photoshop afterwards.
The fourth is also very nice, but again, make sure that you have a flat horizon. It looks pretty even to me, but it may be a slight bit off. It would also be interesting to see a bit less ocean and a bit more land, but that's my personal opinion. Without seeing it both ways I can't tell you which one I think would look better.
This is where a CPL would've done wonders, so keep that in mind for next time.
The last is also my favorite, the lighting is very nice. It really warms up the sand, and gives a nice reflection on the ocean. Nothing to complain about here, you hammered the nail on the head!
By the way, although it's to be expected when shooting at extreme wide angles like in these shots, lots of them seem very distorted around the edges. This may be something to consider when post processing them, the buildings along the sides seen very slanted.
Hopefully I helped,
Gear: 7 Nikon Nikkor AI-S and AF-S lenses, SB-700 flash, Nikon D7000, Nikon FM, variety of accessories
"There are no rules for good photographs, there are only good photographs."
- Ansel Adams