The Belgian Cast is a great cast to have in your salt water cast arsenal. Fishing in the salt means dealing with heavy winds often. Making a cast with that heavy wind blowing hard on your casting side makes taking a even a short cast a major challenge.
The low side back cast of the Belgian cast helps to keep the line low to the water and out of the wind as much as possible. Following with a forward cast that carries the line high over your head that doesn't allow the line to blow into your body and mess up your forward cast.
This cast gives anglers a huge advantage when dealing with strong winds. Check out this video for a demonstration.