Lots of things you can do to improve your photos... indeed taking them is only half the process

You will need an image editing application like Photoshop, or free equivalent
GIMP.
1. Make sure the horizon is level. Photos that involve the sea look very odd when they are at a sloping angle. If you can't get it level in the craft, you can always fix this afterwards in Photoshop etc, though it is better if you can get the camera straight at the time of shooting, because correcting it afterwards will lose resolution...
2. If you can shoot in DNG do. It will look like cr*p initially, but has greater dynamic range, is more suitable for editing, and is a lossless format that doesn't have jpeg compression artefacts.
3. Resolution - take photos at the maximum resolution you have available (4160 x 3120 px) and reduce to the size you need in post-processing, which will enhance detail. Upload to forums like this at 1920 x 1200 px (72 dpi) or similar (each pic can be about 2-3 MB) so we can see all the nice details, but it is not too big for the web.
4. It is very rare that a photo looks as good as it can without post-processing in Photoshop or similar. This can involve (selective) sharpening, levels (or curves), shadow/highlight and saturation adjustments and any colour grading you need to do to make the image better match how it looked to you at the time.
There are tutorials for pretty much every image editing app out there on youtube, and you can often find the most useful ones by adding the terms 'landscape' and 'color grade' into your searches. But here's a good one for beginners...
Hope that helps...