Look for Reflections
Speaking of seas, one of the elements that can immediately come to mind are the reflections. Reflections can help or ruin your composition. It all depends on the scene you have before and especially on what you want to achieve.
It is necessary that your composition has an element of interest that can be reflected on the water. The water itself must be firm enough to create the reflection.
If you notice that the reflection ruins or complicates your composition, you can solve this by using a polarising filter.
Include the Foreground for Unusual Compositions
The vastness of the sea meeting the sky is a beautiful subject to photograph. But it is also overused and sometimes even boring.
So use the foreground to break up this common composition. A rock or a rock formation, a stone that draws stripes on the sand, or a series of rocks worked by the sea are all examples of foreground. Incorporate these in your composition by positioning your camera very low on the ground.
It is obvious that by positioning your tripod and camera very low, your foreground will not only receive attention but will probably also change shape and proportion. And it will do so in relation to the other elements of your composition.
You need to be very careful not to find yourself with a photograph completely unbalanced when it comes to the composition.
Additionally, you should also pay attention to the colours. If you photograph at dawn or at dusk, it is very probable that the sky will be coloured with very intense and warm colours.
It also depends on the atmospheric conditions and the passage of important cloud formations. Keep in mind that your foreground will usually have less intense and sometimes less interesting colours than the sea or the sky.