Kaiyukan

So, the correct answer is that the picture shows jellyfish. Actually, the picture consists of nine distinct photographs that I took in quick succession and then layered on top of each other. The effect is that the composite picture gives some impression of the movement of the jellyfish instead of only showing a static snapshot. Here is another jellyfish photographed using the same technique:

I saw the jellyfish when I was visiting Kaiyukan - Osaka aquarium - a couple of days ago. The aquarium is a very nice and well-designed place. Basically, you start out on the top floor and then spiral down, with fish tanks of various sizes on both sides of the path. This is how it looks like from the outside:

The aquarium's theme is the ring of fire / ring of life represented by the pacific rim, so the natural habitat of all the animals is located somewhere on the pacific rim. The show not only fish, but also otters, penguins, dolphins, seals, turtles - and a few monkeys.

A very interesting feature is that many of the tanks are visible several times from different levels in the building. This makes for a great change of perspective. For example, have a look at these two pictures of the Great Barrier Reef tank. On the top level, you are just below the water surface and what you see there is mostly lots and lots of colorful fish. On the lower level, you are near the bottom of the tank and as you can see it's a completely different atmosphere compared to the top level.

Another very interesting exhibit is the piece of acrylic glass you can see below. I've never really thought about how thick the glass walls are in an aquarium - or how thick they have to be to keep all that water safely where it's supposed to be. The glass they use in Kaiyukan is 30cm thick. Just think about it... 30cm! That's massive!

With regard to Japanese people or culture, the aquarium also has a couple of insights to offer. First, the urge to photograph seems to manifest early in a Japanese kid's life: in front of each and every tank, there were lots and lots of kids taking pictures of as many fish as they possibly could.

Second, there are several photo spots throughout the aquarium. You can pose with model sharks or dolphins, have your picture taken, and pay for your copy of the picture on the way out. Taking pictures with your own camera isn't allowed - seems the aquarium has to make money some way or other...

And, finally, the bottom floor. I've never seen such a huge gift shop in a museum - many, many shelves with stuffed animals and just about any other souvenir you can imagine, all themed around Kaiyukan and its inhabitants. Impressive!