Gemini is a Unity-based visual simulator originally developed by graduate students at NTNU in Trondheim, Norway. The project began as a simulator for the Milliamperé Autonomous ferry. The purpose behind Gemini is to provide a foundation for EMR (Electromagnetic Radiation) based sensors, such as optical cameras, LiDAR and Radar for use in development and testing of autonomous applications. In addition to providing the simulated sensor data from inside the simulation environment, Gemini will expose an API that allows developers to interface and communicate with the simulated vessel(s) and environment. At the moment there does not exist a single executable for Unity and it is only provided as a Unity project. One of the primary goals in the near future is to have a simple release of an executable ready, with all the minimum functionality for operating and interfacing with a simple autonomous vessel.