We developed a small robot with Inline Archimedean Screw Mechanism in response to the demands of surveying Invasive Alien Species (IAS). There are some harmful IAS in wetlands such as snapping turtles. The current method for the survey is net-trap (“Mondori-wana”) and fumbling search by humans. Both methods are inefficient and unsafe for humans. To improve the efficiency and safety of surveying IAS in wetlands, the mobile robot system is demanded. The target environment is configured with soft ground, covered with water, dense water plants and side hole. There is no mobile robot that can move in such an environment. We proposed Inline Archimedean Screw Mechanism to realize locomotion performance at the target environment. The robot can move on a soft land as if cutting a screw. Furthermore, pushing aside water plants, the robot can prevent itself from getting stuck by dense water plants. Using Inline Archimedean Screw Mechanism, we developed the robot, named WANGOT (WAseda Native species Guardian robOT). WANGOT has the size of W85 × H85 × L460 [mm], the weight of 1.4 [kg] and two actuators and four Archimedean screws. It was possible to move forward at a speed of 27 [mm/s] on artificial turf, and the movement performance on the environment of simulated dense water plant area was confirmed.