How We Know

Ocean zone

Sunlight Zone

Epipelagic · 0–200 m

Reference answer

The upper ocean where photosynthesis can occur and most familiar marine food webs begin.

LightBright to dim natural sunlight
TemperatureHighly variable
Pressure at base≈ 21 atm

Defining conditions

  • Enough light for photosynthesis
  • Strongest daily and seasonal temperature changes
  • Highest direct connection to weather and atmosphere

Representative creatures

Frilled sharkA rare eel-shaped shark with six pairs of gill slits, three-pronged teeth, and flexible jaws.

Evidence

Sources reviewed

  1. Ocean zonesWoods Hole Oceanographic Institution · checked 2026-07-30
  2. The Deep SeaSmithsonian Ocean · checked 2026-07-30