Long Beach Aquarium (Aquarium of the Pacific), Los Angeles
Address 100 Aquarium Way, Long Beach, CA 90802 Map, Tel (562) 590-3100 Call, Discount Purchase tickets online for a $5 discount. Website
This is one of the most spectacular aquariums I have been to. It's HUGE, so using a carrier for little ones is advisable. Tons of exhibits of all types of sea creatures, has both inside and outside exhibits. Highlights include Shark Lagoon, touch tanks with rays, and a 180 degree walk through tank that is amazing.
It's on the water and a short walk to a nearby area with fun restaurants and shops, too.
Word of advice: it's crowded. My 2 year old daughter and I went on a weekday and it was jammed with kids on school field trips. I imagine summer and weekends are busy as well. My suggestion would be to go mid-week, during the school year, in the afternoon if possible. (All the field trip buses had departed by 1pm.)