SPAWAR Systems developed this sea water antenna that uses a jet of water and current probe instead of a metal pole as a transmitting element. I don’t doubt that it works, howver I’m skeptical about how practical the idea is — you’ll need to have a beefy energy source to run a pump, and turbulent weather seems like it would be an issue. Still, the idea of a fluid-based antenna seems great, and might provide for lots of other interesting applications. How about a water fountain Theremin? [Thanks, Matt!]