It doesn't matter how many war machines you have under your command if you can't relay orders to their operators. Maintaining communications is just as important as firepower, and DARPA wants the armed forces to have as many contingencies as possible when networks go down or are actively jammed. Setting up a fallback network is even trickier on the open ocean, but the agency's Tactical Undersea Network Architecture (TUNA) program is well on its way to a solution. That solution being a collection of "node" buoys, deployed from ships or planes, that are tethered together by fiber optic cables to create a radio frequency data network.
The fiber cables connecting the buoys may be thin, but are being developed to survive 30 days in challenging underwater environments, which should cover the time it takes to restore normal comms. Powering the network presents another problem, though the University of Washington's Applied Physics Lab have created a concept buoy that draws energy from the constant ebb and flow of the ocean. The TUNA program has been in DARPA's pipeline for the past few years, and with the first phase now complete, the next step is to build a fully working system and test it at sea.
DARPA's seafaring solution compliments another ongoing program called Dynamic Network Adaptation for Mission Optimization (DyNAMO). Its goal is to develop a system that allows all different types of equipment found in different types of aircraft to talk to each other, creating something of a peer-to-peer communications network in the sky.