Why do deep-sea fish survive pressure?

Answer: No air spaces in bodies

Thick armor-like scales — Wrong. Thick scales don't protect against pressure. Deep-sea fish survive by not having air-filled spaces that would be crushed.

Air pockets compress evenly — Wrong. Air pockets would be crushed at depth. Deep-sea fish specifically avoid air spaces—their swim bladders are reduced or absent.

No air spaces in bodies ✓ — Correct! At extreme depths (1000+ meters), pressure exceeds 100 atmospheres. Deep-sea fish lack swim bladders (air-filled organs) and have gel-like, water-filled tissues. Since water doesn't compress, internal and external pressures equalize. Their bodies are designed to have no compressible spaces!