One of the most photographed scenes in the world is the beach scene. The reason is that (a) the locale is beautiful by nature, (b) people are usually relaxed and having fun and are not "stiff" and (c) a combination of the first two reasons. This means that beach photography can be either landscape or portrait photography or a combination of both.
Unlike most other forms of photography, beach photography is about movement. The water is always in motion and if this plays a major part in the composition, you have to be able to balance this movement with the stillness of the rest of the image. The best way to do this is to keep the amount of motion in mind. If there is crashing surf, you will be best served by limiting the amount of surf in your composition or it may overshadow the non moving parts. The less the water movement, the more of it you can include in your compositions.
In beach photography, light is not always your best friend. We are accustomed to seeing bright sunlight in beach photos. But remember that if there is white sand, it can cause a lot of glare and result in stark high contrast photos that do not capture the feel of the beach. As in all landscape photography, the best time to shoot is in the mornings and evening when the light hits the sand obliquely, resulting in less glare and harshness and thus warmer colors.
Beach photography is really all a matter of perspective and the best way to learn how to use the flatness of the land and water to your advantage is to keep experimenting with distances and depth of field.