Abstract: Systems, devices, and methods for laser-based communications are disclosed. At least one embodiment relates to laser-mediated underwater communications, in which one or more laser signals transmit encoded information from a transmitter to a receiver. Additionally, an underwater transmitter node sends information to an underwater receiver node using one or more lasers. At least an additional embodiment relates to laser-based communications that may be used to send information across a variety of media (e.g., air, water, etc.). Specifically, a first and a second communications system each sends a laser beam to the other. Each communications system further includes a position sensitive detector (PSD) that obtains positioning and/or steering information of an incoming laser beam and ensures that the positions of both the outgoing laser beam and the incoming laser beam match.