Glass fibre reinforced composite facings on PVC (poly(vinyl chloride)) foam cores are widely used sandwich materials in boat structures, but life cycle analysis suggests that alternative materials may be preferable for the environment. However, in order to design with these alternative materials their mechanical behaviour must be characterized and understood. This paper describes an experimental campaign to evaluate the performance of alternative sandwich materials with reduced environmental impact, under loading conditions relevant to boat design. Flax and bamboo composite faced PET (poly(ethylene terephthalate)) foam sandwich materials are compared to the current PVC foam sandwich on a constant weight basis. A series of quasi-static tests is described first and analysed. Then hard and soft impact tests are described, which allow a comparison to be made between existing and alternative sandwich options. The results indicate that the alternative materials show lower flexural stiffness. Damage initiation levels are also lower, but the impact energy levels they can support are promising, and facing improvements could raise these further.