A selectively submersible vessel includes a combustor, a Stirling engine thermally coupled with the combustor, an electric generator mechanically coupled with the Stirling engine, a rechargeable battery electrically connected with the electric generator, a compressor electrically coupled with the rechargeable battery, a ballast tank fluidly coupled with the compressor, a snorkel fluidly coupled with the compressor, a controller electrically connected with the rechargeable battery, at least one sensor electrically connected with the controller, a data storage device electrically connected with the controller, and a data communications device electrically connected with the controller.