An improved benthic microbial fuel cell for generating energy at the interface of aquatic sediment and seawater includes an anode electrode embedded within the aquatic sediment, a cathode electrode positioned within the seawater and above the aquatic sediment, a rig for maintaining the relative positions of the anode and cathode electrodes, electrical leads extending from the anode and cathode electrodes to a load, wherein the anode electrode comprises a bottlebrush electrode residing within a permeable tube. The apparatus is easier to deploy than previously-described fuel cells, while being lighter, more durable, and generating greater power density. Also disclosed are methods of generating power from such an apparatus.