Adjective may be more rigid in some languages than others; in some, like Spanish, it may only be a default ("unmarked") word order, with other orders being permissible. Other languages, such as Tagalog, follow their adjectival orders as rigidly as English. The normal adjectival order of English may be overridden in certain circumstances, especially when one adjective is being fronted. In addition, the usual order of adjectives in English would result in the phrase "the bad big wolf" (opinion before size), but instead the usual phrase is "the big bad wolf", perhaps because the ablaut reduplication rule that high vowels precede
Aquatic animal animals). However, the adjective marine is most commonly used for animals that live in saltwater, i.e. in oceans, seas, etc. Aquatic animals (especially freshwater animals) are often of special concern to conservationists because of the fragility of their environments. Aquatic animals are subject to pressure from overfishing, destructive fishing, marine pollution and climate change. In addition to water breathing animals, e.g., fish, most mollusks etc., the term "aquatic animal" can be applied to air-breathing aquatic or sea mammals such as those in the orders Cetacea (whales) and Sirenia (sea cows), which cannot survive on land, as well as the pinnipeds