Subsea View of Inverted Helical Grooves on Drill Riser Buoyancy.Image: Trelleborgwww.marinetechnologynews.comMarine Technology Reporter 43MTR #4 (34-49).indd 43 MTR #4 (34-49).indd 43 5/10/2018 9:45:39 AM5/10/2018 9:45:39 AM