Your wife should be congratulated on excellent choice of toe-nail paint . The pinkish hue truly compliments that lovely sunset.

Don't put your subject in the middle of the frame. Putting the subject about one third of the way in from the side of the photo will give your shot more balance and be a more pleasing composition to the viewer. In this case I would have put the subject to the right of the shot, so she is looking out over the rest of the image. Google "rule of thirds" for more info.

The sky looks nice and I would have liked to have seen more of it (rule of thirds again), so about 30% sky, the rest sea and subject etc.

Yeah, the horizon either 33 % from the top or 33 % from the bottom. Stupid rules but they work wery good.

In this case you should tried to take the photo from a much lower position to get more of the sky because that is more interesting than the water.

But I like the colors and I like the way you used the flash.

So a very good photo but just cropped a little bit from the standard rule.

I'm not a pro but I do like it.

I like your composition as your wife is in the area of the photo not reflecting the light from the sky and the foreground adds some interest to the photo. Rules are made to be broken as long as you understand that they exist and why they are recommended. Then follow your own instincts as long as it speaks to you. The biggest problem in your picture is the digital noise from either a small chip, high ISO, under exposure or all of the above. Some of this can be corrected in photoshop while most of it is inherent in the equipment and the low light. Using exposure compensation for the over all exposure (minus) and the flash(plus) would help if your camera allows you to do that. I hope this helps you.