The principal feature of all dredgers in this category is that the loosened material is raised from its in-situ state in suspension through a pipe system connected to a centrifugal pump. Various means can be employed to achieve the initial loosening of the material. If it is naturally very loose, suction alone may be sufficient, but firmer material may require mechanical loosening or the use of water jets. Hydraulic dredging is most efficient when working with fine materials, because they can easily be held in suspension. Coarser materials – and even gravel – can be worked but with a for greater
demand on pump power and with greater wear on pumps and pipes.