Butter 

Butter, or the "Type 76QY Autonomous Littoral Surveillance System," is a fictional amphibious robot featured in Peter W. Singer and August Cole's 2015 novel, Ghost Fleet.  In the novel, the small lobster-shaped robot accompanies a Navy SEAL element on a direct action mission on the island of Oahu, Hawaii.

The multi-mission robot is alternatively an assassin, intelligence collector, patrolling perimeter defense system, communications relay, and electronic jammer.  It's arthropod-like artificial intelligence enables it to navigate autonomously and even conceal itself from threats when required.  

Butter has cameras to surveil targets and can link its streaming video to the SEALs via a line of sight laser system. It also can fire a short range anti-personnel dart filled with genetically-modified sea snake poison.  After climbing a high antenna using elastomer adhesive on its legs, the robot crustacean becomes a long range voice and data communications relay for the SEALs to designate targets for the fleet operating well offshore. Butter then jams enemy communications.

Ghost Fleet and Future Unmanned Naval Warfare

The Real RoboLobster

U.S. Navy Photo

According to the book's footnotes, Butter is loosely based on a biomimetic lobster robot developed by Northeastern University's Marine Science Center and industry partners for DARPA's Defense Science Office and later the Office of Naval Research (ONR).  That Robolobster, which was about two feet long and weighed seven pounds, was designed to survey river bottoms and surf zones for mines.  The robot's eight legs used an artificial muscle, called Nitinol, enabling it to crawl on the ocean floor or land, and two fiber-optic antennae. Joseph Ayers, a professor of biology and director of external relations at Northeastern University’s Marine Science Center in Nahant, Massachusetts, began developing the RoboLobster in 1998. The RoboLobster was named one of Time magazine’s Coolest Inventions in 2003. 

The RoboLobster was just one of many U.S. military-sponsored biomimetic drone projects.  Others include Ghostswimmer (derived from Boston Robotics BioSwimmer), and the jellyfish Cyro.  The Central Intelligence Agency also developed a bio-inspired spy fish called Charlie.