A composition is provided for producing a 3-D printable material comprised of a marine biodegradable base polymer and a gelling agent in a ratio preselected to achieve a desired rate of degradation of a structure printed from the material. Suitable polymers include polycaprolactone (PCL), polyhydroxyalkanoate (PHA), or polybutylene succinate (PBS). The gelling agent is typically agar. Faster rates of degradation of the structure are obtained with larger proportions of gelling agent in the composition. The composition may also include biological materials to further promote or control the biodegradation of the structure, and other additives such as nutrients for microorganisms or solidifying agents. 3-D printing of the material occurs at relatively lower temperatures to avoid damage to the biological materials.