The term oceanarium is not well defined. It can either mean a marine mammal park such as Marineland of Florida or a large-scale aquarium such as the Lisbon Oceanarium presenting an ocean habitat with marine animals, especially large ocean dwellers (e.g. sharks).
Marineland of Florida, one of the first theme parks in Florida, USA, started in 1938, claims to be "the world's first oceanarium", while Ocean Park in Hong Kong claims to be "the world's largest oceanarium".