We became familiar with the Seattle Aquarium after our daughter decided to volunteer there during high school. She enjoyed it so much, that she continued leading tours and volunteering until she was too old (19). The Aquarium has a number of unusual exhibits from ultra-rare leafy sea dragons to huge octopi, to baby sea otters. It's an enjoyable way to spend an afternoon, and the kids love the hands on tidal pools. Just be aware - when they say "No Smoking" on the dock, they are *serious*! ;-)
There is also an Imax theater attached.
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