This article reports on an underwater robot that searches for chemical sources in stagnant water. Biological studies suggest that crayfish in search of foods generate water currents by using their fan organs (maxillipeds). The proposed robot is equipped with two pairs of fanning arms mimicking crayfish maxillipeds. The chemical substance staying near the floor is stirred up by the water currents generated by the second pair of fanning arms, and then, is collected to the chemical sensors by the inflow generated by the first pair of arms. Experimental results are presented to show that adding the second pair of fanning arms significantly improves the chemical detection ability of the robot and therefore the success rate of the chemical source localization. These results suggest that active flow generation is essential for crayfish to search for foods by tracking their smells.