A float for a steel pipe surface dredging line formed of snugly fitting inner and outer sleeves (1,2) each of which are composed of two sleeve parts (3, 4) and (5, 6) respectively.
The construction as described, may be readily dismantled in use. This is advantageous and cost saving, in that it means for example that the whole unit does not have to be discarded when localised damage occurs as in the prior art, rather only that particular part damaged i.e. one of the outer sleeve parts, has to be replaced. Moreover since the inner sleeve (2) may constitute 60% of the buoyancy required, loss of buoyancy due to outer sleeve damage does not render the whole unit ineffective as is possible with single shelled units known in the prior art.
The sleeves (1,2) which are hollow, may be either foam filled, of strengthened with internal struts (101). With this latter construction a port P in the outer sleeve 2 may be provided so that the sleeve can be selectively filled with water, for example, so varying the buoyancy on site.