Sea plastic waste is a big issue and cleaning them is very important. We are developing a USV cleaner that collects plastic waste for cleaning at the port. There are many ships in the port and the USV needs to design a collision avoidance procedure appropriately. To develop a collision avoidance procedure, several experiments must be performed. In this paper, we will first introduce a low-cost tank experiment system to study USV collision avoidance procedures. This system consists of a ceiling camera and a robotic ship. The ceiling camera is installed above the tank and uses image processing to calculate the heading and COG coordinates of each ship. This is intended to emulate GNSS indoors. The catamaran was designed and manufactured using a 3D printer, taking into account the size of the tank and the capacity of the ship. The catamaran has a single board computer and a wireless communication device. Each ship receives coordinates via wireless communication from a computer that calculates the coordinates in the tank. Next, the results of tank experiments using the above system are introduced. When the experiment starts, the ceiling camera calculates the ship's position and sends the position data to each ship in increments of 10 [Hz]. When the ship receives the position, it moves forward while maintaining the bow and speed until a collision is detected. When each ship finds a possible collision, it changes the navigation mode from normal mode to collision avoidance mode. This experiment confirmed that the ceiling camera position detection, catamaran thrust, and wireless communication were all functioning properly. Finally, we introduce the conceptual design of the Catamaran USV used to clean plastic waste in port areas.