Marine energy potential across US coasts depends on technologies such as turbine blades, which rely heavily on composite materials. These materials are needed to survive the harsh marine environment in terms of physical and environmental damage to equipment in service. In this study, we developed a bio-based epoxy resin combined with North Carolina-grown natural fibers to fabricate composite panels for structural and functional marine applications. The resin is made from bio-based monomers with minimal chemical waste and a very low curing temperature (100–200 °C). Three different approaches to making the resin from DGMeOHQ were explored: acid (CYCAT)-catalyzed epoxy-phenol, base (PPh3)-catalyzed epoxy-phenol, and isophorone diamine (IPDA)-hardener. Thermal and tensile properties were tested for both epoxy films and composite panels. The ones made using IPDA-hardener proved to demonstrate better results overall. Also, composite panels of larger dimensions with scaled-up amounts of resin were fabricated using a special mold and heat press for curing. Separate panels were made using combinations of the bio-based resin with flax fiber, the bio-based resin with commercial glass fiber, and commercial prepregs for comparison. These panels are cut into specimens for further testing according to ASTM standards, with one batch undergoing moisture submersion before testing. Results show that the bio-based epoxy system exhibits superior after-cure thermo-mechanical properties compared to petroleum-based epoxy systems. The results from the study provide a foundation for the use of completely bio-based composites for marine hydrokinetic applications with recycling and upcycling potential.