Aquamarine Fukushima is Iwaki's easiest crowd-pleaser: a large aquarium at Onahama that focuses on water environments rather than just tanks of famous animals. Exhibits move from rivers and coasts to the Pacific, with enough scale for a relaxed half day.
It is especially good in bad weather or with children, but it is not only a family fallback. The building and habitat approach make it one of coastal Fukushima's strongest modern sights.