  Autonomous multi-agent systems are increasingly being deployed in
environments where winds and ocean currents have a significant influence.
Recent work has developed control policies for single agents that leverage
flows to achieve their objectives in dynamic environments. However, in
multi-agent systems, these flows can cause agents to collide or drift apart and
lose direct inter-agent communications, especially when agents have low
propulsion capabilities. To address these challenges, we propose a hierarchical
multi-agent control approach that allows arbitrary single-agent performance
policies that are unaware of other agents to be used in multi-agent systems
while ensuring safe operation. We first develop a safety controller using
potential functions, solely dedicated to avoiding collisions and maintaining
inter-agent communication. Next, we design a low-interference safe interaction
(LISIC) policy that trades off the performance policy and the safety control to
ensure safe and performant operation. Specifically, when the agents are at an
appropriate distance, LISIC prioritizes the performance policy while smoothly
increasing the safety controller when necessary. We prove that under mild
assumptions on the flows experienced by the agents, our approach can guarantee
safety. Additionally, we demonstrate the effectiveness of our method in
realistic settings through an extensive empirical analysis with simulations of
fleets of underactuated autonomous surface vehicles operating in dynamic ocean
currents where these assumptions do not always hold.
