FRP is used the materials of boat or yacht. But, FRP boat is apt to be laminated imperfectly and becomes heavier than its initial weight due to sea water absorption of core material. Therefore, alternatives of FRP has been proposed by many boat builders and high strength aluminium is considered as its standard material. But, high strength aluminium is very expensive as boat material. Therefore, in this study, we evaluated the application possibility of an inexpensive polyethylene as boat material.