A vessel should follow a planned route. However, when a target ship deviates from its original track, the subject ship should maneuver to avoid a ship-to-ship collision. This paper presents a trial maneuver-based method for collision avoidance that considers the potential area of water (PAW) for maneuvering that is available to the target ship. The initial conditions, including the position, speed, rudder angle, drift angle, and yaw rate of the target ship, are derived from automatic identification system (AIS) data. AIS data from Madura Strait were used to simulate collision avoidance. The PAW of the target ship was predicted based on a probability distribution of the initial conditions using a mathematical maneuvering group (MMG) model. Finally, a trial maneuver method for the subject ship was simulated to avoid a ship-to-ship collision. The MMG model for the simulation was developed to consider the effects of shallow water and wind and current disturbances.