Figure of eight
These booms have excellent wave following characteristics, they are constructed from two independent chambers, the upper of air and below of water. These booms require a constant flow of air and water while it is deployed. An air fan and water pump work continuously. In the event of a problem with the flow of air, the boom will sink. When deploying if there is insufficient weight of water in the boom they have been known to fly in windy conditions. This is an old design which is not common anymore due to its disadvantages outweighing the advantages.