components such as those disclosed in u s pat no 5 900 195 the composition 62 formed by such a reaction is as a result a high density rapid setting polypropylene or polyurethane foam system 62 the foam 62 serves as a shock absorber and protects the corrosion coating on the pipe 24 26 also because the foam 62 is open celled it can absorb water and increase the ballast effect for the pipeline 10 alternatively other polymerizing or hard setting compounds such as marine mastics quick setting concretes polymers or elastomeric compounds may be used to fill the annular space 54 any alternative filler substance 62 typically is quick hardening such that the process of laying the pipeline 10 is not inhibited the preferred polyurethane or polypropylene system utilized to form the protective high density foam 62 in this process is a combination of an isocyanate and a polyol system when reacted this combination system rapidly cures and forms high density open celled polyurethane or polypropylene foam 62 which resists degradation in seawater the isocyanate is a polymeric form of diphenylmethane diisocyanate as manufactured for example by bayer corp the preferred polyol system is a mixture of multifunctional polyether and or polyester polyols catalysts.