Nice to have the Seattle Aquarium right on the Waterfront. It is packed full of different exhibits AND hordes of tourists/families/kids. Rather confusing lay-out, like a rabbit-warren. Claustrophobic.
I liked the Dome where divers feed the fish at about 1:30 in the afternoon, as well as the otters and seals. And the hall in which one can actually touch and feel the sea-slugs, starfish, and the stunning, chrysanthemum-like anemone.
But for my money, a trip to the Woodland Park Zoo--mostly out in the open--makes the Aquarium pale in comparison, especially in summer, though, of course, we shouldn't be comparing...