Miyajima Public Aquarium is a compact family stop on the island, about a 20-minute walk from the ferry pier and close enough to combine with Itsukushima Shrine. The exhibits focus on sea life from the Seto Inland Sea along with other marine animals.
It is most useful if you are visiting Miyajima with children or want a break from temples and shrine crowds. Daily animal presentations add some structure to a short visit.