I like synthetic biologicals, drone whales, they look like whales, they have an exact acoustical signature as a whale, they can blend in with a herd.
But they can launch rocket powered anti ship torpedoes, nuclear tipped if needed.
Or syn dolphins, but instead are themselves anti ship mines.
And if you truly want to demoralize the enemy you create a huge robotic Kraken, ship sized.
This is sad.
The army under funded and looking for strange solutions to well known problems
The Army is looking at ways to modify existing systems to do some radically new things like howitzers shooting shells at ships....
Been there, done that: it was called Coast Artillery Branch.