Category Nuances for null:

• polar,
• larger,
• marine,
• real,
• large,
• new,
• toothed,
• captive,
• small,
• opportunistic,
• wild,
• arctic,
• underwater,

Simple Categories for null:

• cetacean,
• mammal,
• feeder,
• animal,
• whale,
• inhabitant,
• creature,