The company developed a special nozzle to spew out the seawater plumes, since they need to be insulated to work. It also had to determine the plume diameter ideal for transmitting signals and managed to compute for a size that achieves a 70 percent efficiency. Since SeaAerial is comprised of only two components (a pump and an insulated nozzle), it can be installed anywhere where seawater is accessible. In the future, they could be built on shores, in the middle of the sea or even on land if the company can figure out how to contain and recycle the water it's using.

Update: Google also developed a seawater antenna in 2009, as you can see in this YouTube video. [Thanks for the tip, Stephen Rusboldt!]