The building where the aquarium is located was built initially as a natatorium in the 1920s,[1] an indoor saltwater public bath,[2] with the water pumped from the Pacific Ocean through a pipe still visible today at the tide line, and then heated.

The building later served as a salmon rearing facility and then a place to watch wrestling matches.

The Seaside Aquarium reports 100 species of marine life including 20-"arm" sea stars, crabs, wolf eels, moray eels, and octopuses.

[4] During March 2013, a boat lost during the 2011 Tōhoku earthquake and tsunami drifted across the Pacific Ocean and washed up on the shores of Washington carrying trapped live fish.

The sole remaining so-called tsunami fish was put on display at the Seaside Aquarium.