I've been a couple of times and a whole day is not enough for me. You simply must go. I'm awestruck by the "Blue Cavern" exhibit, a 142,000 three-story high exhibit--fishes and other sea creatures which are found off the coat of Catalina and S. California waters--you could stand there for an hour just staring.
There is so much to see; I’d never seen the rushing waters--the exhibit which shows those creatures which inhabit the cold moving waters, the "surge channel".
Yes, there is the Discovery Lab and the Ray Touch Pool, but when we were there, there was also that wonderful rainforest habitat, where we lorikeets came to alight on our arms and where we could give them sugar water. Oh, my, that was great. Have you ever seen a more colorful and cheerful little bird?
Go to the Shark Lagoon, but I prefer "tropical Pacific Overview" or "Northern Pacific". Look at humungous lobsters, or sea turtles, or shore birds, or kelp fish, or sea otters. Well, spend the day. Eat there, go to the gift shop, and bring lots of ASA 800 film.
And if you stay overnight in Long Beach-well, just stay overnight on the Queen Mary, it is a great experience and she is right there. Imagine spending the day in the Aquarium of the Pacific and the night on the really-truly Queen Mary. You know it is very reasonable in the winter!