Hi Keat, you have a great image that has captured the 'layers of colours' you were shooting for. The beach does help add depth. The key to applying HDR technique is to not have the viewer notice the HDR, but rather think of the image in terms of what they would expect to see in a pleasing image. I feel that you have done very well in that aspect here.
There are a couple of things you could consider. First, the horizon is almost at the halfway mark in the image, dividing the image in half. There is more solid blue sky with nothing in it than needs to be in this kind of an image. Third, wide horizontal lines in a landscape can sometimes benefit from a 2:1 ratio, that is, a crop where the image is twice as wide as it is tall. This can create an expansive feeling as big as the great outdoors.
There is an alternative 'rule of thirds' that can often be applied to a landscape image and that is 'put something interesting in each (vertical) third of the image'.
All of these concerns can be addressed with a simple crop. Consider removing enough sky to put the horizon at approximately the 2/3 line up from the bottom. That will place the dramatic sky in the top third without losing any of the detail in the sunset lit clouds. Next, play with cropping the beach only as much as necessary to achieve the 2:1 ratio and retain the majority of the water in the center third of the image. You may end up not needing to crop any of the beach as long as you can get the 2:1 ratio and have approximately 2/3rds of the image from the horizon down. This will leave you with the beach in the bottom third to provide the feeling of depth, and the sand bar, majority of the water, and the sky reflections in the middle third for interest. Hope this helps!