His left arm still dangled in the water , and the thing- whatever it was he 'd mistaken for a fish , was still holding it . The light bounced in ripples over its body , illuminating it , but it was n't for another long moment that Atobe saw the tail . " Thank you , " Atobe mouthed to it and its eyes flicked , watching his face , trying to understand . It ... he , whistled and tugged gently on his arm .
Question: Why did Atobe do this ?
The answer to the above question:


He was trying to catch a fish