Photo by Michael Gonzalez Engineers work on setting up the aerostat balloon that floats above the Thunder Bay National Marine Sanctuary on Thursday afternoon. The balloon is for the Department of Defense event Silent Swarm and helps link the project's boats on Thunder Bay to the Great Lakes Maritime Heritage Center. According to Jonathan Thurston, an engineer working on the balloon, it acts like a cell tower for their electronics out on the water and boosts signals to go further distances. They also have an U.S. flag on the balloon to diminish any worries.