<p>Bio-logging is a method using small data loggers attached to the bodies of animals to acquire behavioral information. Zoologists are trying to capture video data of preying sperm whales using the method, but no one has succeeded. They can put a data logger only on the back of sperm whale. Even if data logger is attached to the back, they can't take a video of the mouth area because of the darkness of the deep sea. To tackle the problem, we have introduced a "Whale Rover" that moves along the body surface from the back to the mouth area. In this paper, we confirm the feasibility of the current prototype through experiments in the deep sea.</p>