Time to go in another direction. The clue is a picture of a moonfish, less specifically a fish.
No one has mentioned that the term "fish" is used by the Navy as slang for a torpedo.
"Fish" is also slang used by civilian treasure hunters and geoscientists to refer to a towed sensor such as a magnatometer or side scan sonar. Both of which are often used to locate sunken ships which might have been sunk by torpedos.
Originally, torpedos were not the propelled ordinance they are today, but were simply sea mines.
Sea mines often have magnet detonators.
Mine clearing operations are an excellent task for robots.
Mines are also a source of treasure.
A torpedo is also a type of short level often used to level or plumb conduit.
Maybe these are all just Red Herrings, but word association can be beneficial.
