Osaka Kaiyukan Aquarium

For 2400 yen, you can get a Kaiyu Pass for the day at the Osaka tourist offices (e.g. one in the Namba station) which includes the admission to the aquarium (2000 Yen separately) and unlimited subway in Osaka for the day. The aquarium is in Osaka harbor, a very nice big building, colorfully decorated, there are other sights to see near it too, such as the Suntory Museum and its IMAX theatre. The biggest attraction at this aquarium are the whale sharks. I don't know if any other aquariums in the world had whale sharks, but this is the first time I saw them in person. These were 2 relatively small ones only more than 4 meters long, but they were definitely the biggest fish in the tank! It was very relaxing to watch them swim by, with their school of smaller fish friends.
The aquarium had many tanks, devoted to different areas of the Pacific Rim. the ring of fire. So there is a lot to see. The dolphins were fun to watch too, as were the penguins. Plan to stay about 2 hours at the aquarium.