1.
marine mammal
A mammal that lives primarily in the ocean, such as seals, sea lions, walruses, and sea otters. A zoological term.
Composed of 海 (sea) + 獣 (beast, animal). Refers specifically to marine mammals — not fish or other sea creatures. Includes animals like アザラシ (seal), アシカ (sea lion), セイウチ (walrus), ラッコ (sea otter), and sometimes クジラ (whale) and イルカ (dolphin). Not to be confused with the homophone 怪獣 (monster, as in Godzilla). Common collocations: 海獣類 (marine mammals as a group), 海獣ショー (marine mammal show). In Japanese aquariums, the 海獣 section typically features pinnipeds (seals and sea lions).