Aquarium of the Bay San Francisco. A moving walkway takes you through 300 feet of clear tunnel surrounded by the Bay's inhabitants, like the leopard shark, whose numbers have been depleted by pollution. (888) 732-3483, www.aquariumofthebay.com.

Aquarium of the Pacific Long Beach, Calif. Get close to the Pacific's denizens, from giant Japanese spider crabs in icy waters to thick-lipped humphead wrasses puttering around a Palauan rock island. (562) 590-3100, www.aquariumofpacific.org.

Birch Aquarium at Scripps San Diego. Interact with displays inspired by research at the Scripps Institution of Oceanography. The Ocean Supermarket reveals what sea ingredients your favorite products contain. (858) 534-3474, www.aquarium.ucsd.edu.

Maui Ocean Center Maalaea, Hawaii. From the Discovery Pool's porcupine puffer fish to a gregarious spotted eagle ray flaunting its four-foot wingspan, Hawaii's endemic fish all exude the aloha spirit. (808) 270-7000, www.mauioceancenter.com.

Monterey Bay Aquarium Monterey, Calif. This famous institution is a showcase for sharks, sea turtles, dense kelp forests, tide pools, and even sea-inspired art (see "The Art of the Sea," page 25). (831) 648-4888, www.mbayaq.org.

Oregon Coast Aquarium Newport. Watch an improvised ballet by a jellyfish ensemble, see a sea otter get frisky, or walk through a tunnel where sharks and skates swim all around you. (541) 867-3474, www.aquarium.org.

Seattle Aquarium Lootas, a frolicking 4-year-old sea otter, has celebrity status with visitors, but the sturgeon, mighty chinook salmon, and ugly-faced wolf eels also put on a great show in an underwater dome. (206) 386-4320, www.seattleaquarium.org.

Shark Reef Las Vegas. Set in a sunken ancient temple worthy of Indiana Jones, this aquarium abounds with dangerous creatures—from a water monitor known to unearth corpses to a highly venomous stonefish. (702) 632-4555, www.mandalaybay.com.