Pinnipedia is a scientific term that refers to a group of marine mammals, commonly known as seals, sea lions, and walruses. If you are writing an essay or article about these aquatic creatures and want to use a different term, you can choose from several synonyms. Some of the alternatives include sealife, marine mammals, marine animals, pinniped, otariid, phocid, and odobenid. Each term carries a unique connotation and adds variation to your writing. However, it's important to choose the appropriate synonym based on the context and purpose of your writing.