riser joint 12 further other stop means such as a stop screw not shown may be used to engage the foam element 40 and prevent vertical displacement along the riser joint 12 while fig4 depicts only the lower foam element 40 as being equipped with a stop to fix it axially about the riser joint 12 it will be appreciated that each foam element 40 may be so equipped to fix its movement axially along the riser joint 12 alternatively the torroid elements 40 may be manufactured in half sections and secured about the riser joint 12 with bolts and inserts for he bolt make up area and seams not shown much the same as shown in fig2 each of the above embodiments discloses the use of a syntactic foam element to provide buoyancy however it will be appreciated that while the surface of the syntactic foam may be relatively smooth the surface roughness of the foam elements may be sufficiently high as to produce small vortexes in response to ocean currents when installed in a subsea environment in order to improve the smoothness of the foam elements 24 30 and 40 the syntactic foam may be treated with various coatings so as to improve the smoothness of the surface of the foam elements 24 30 and 40 thereby reducing the drag coefficient of each element one typical coating which can be applied to a foam element would be fiberglass gel which would be.