Who Smarted? – "Do Fish Have Eyelids?" (March 23, 2026)

An Educational Podcast for Kids

Episode Overview

This lively episode of “Who Smarted?” explores the fascinating world of aquatic animal sleep, focusing on fish and their unusual sleeping patterns. The hosts dive into questions like: Do fish have eyelids? Do all underwater creatures sleep? And if so, how? Blending humor, storytelling, and science, the episode offers kids (and curious adults) surprising facts about sea creatures' rest habits—plus fun insights into jellyfish, dolphins, sharks, and more.

Key Discussion Points & Insights

1. Do Fish Have Eyelids?

• Main Fact: Fish do not have eyelids.
  • “Just like fish, they don’t have eyelids. So when they sleep during the day, usually wedged between rocks or coral reefs, their eyes appear to be wide open.” – Narrator (04:07)
• Moray eels are nocturnal (sleep during the day, hunt at night) and also lack eyelids, making them seem always awake.

2. How Do Fish Sleep?

• Fish Rest Patterns: Fish don’t sleep like humans. Instead, they have short periods of rest.
  • “For fish, it’s more like short periods of rest than a long slumber. Some fish float in place, others wedge themselves into mud or coral, and some even find a suitable nest.” – Narrator (04:26)
• Sleep is essential for fish to recharge, just like humans.

3. Sharks and Whale Rest Myths

• Many believe sharks never sleep because they must keep moving:
  • “It’s often repeated that sharks never sleep because they have to keep moving to stay alive. But is it true? Nope… nurse sharks can be completely still while sleeping.” – Narrator (04:47)

4. Unique Sea Creature Sleep Adaptations

• Parrotfish: Sleep in a self-made mucus “sleeping bag” to protect from predators.
  • “When it’s time for the parrotfish to go to sleep, it oozes out a jelly-like substance… like a sleeping bag.” – Narrator (05:24)
• Marine Mammals—Whales and Dolphins:
  • Sleep with one eye open and one half of their brain awake (unihemispheric sleep).
    • “When a whale or dolphin goes to sleep, only half their brain shuts down and only one eye closes.” – Narrator (06:15)
    • “It’s the opposite eye from whichever half of their brain shuts down.” (06:25)
  • Must remain conscious to breathe, unlike humans who breathe involuntarily while asleep (07:03).
  • Alternate which side of their brain and eye rest every two hours.

5. Jellyfish: The No-Brainers

• Jellyfish have no brains or central nervous systems.
  • “No, I’m saying the jellyfish is a no-brainer because it has no brain.” – Becky (10:10)
• Despite lacking a brain, jellyfish experience rest and show signs of sleep:
  • “Even though jellyfish lack some of the essential organs and systems that nearly all other creatures have, they too need to catch some Z's after a hard day swimming around the ocean…” – Becky (11:56)
• Scientists test rest in jellyfish by disrupting them and observing slower activity, much like sleep-deprived animals (11:40–12:12).

6. Other Cool Aquatic Sleep Habits

• Walruses: Inflatable air sacs in their necks serve as floaties while they sleep (12:15–12:28).
• Seahorses: Use their tails to anchor to coral or sea plants during sleep.
• Baby Sea Otters: Hold hands with moms to avoid drifting away.
• Sea Stars: Suction onto rocks with their arms at rest.
• Octopuses: Have “quiet” (motionless) and “active” (changing color, moving eyes) sleep states.

7. Goldfish: Do Pets Sleep?

• Goldfish sleep by reducing activity and staying still, not by lying down.
  • “Like all fish, goldfish do not lie down when they sleep. Rather, they become less active, staying in one place and moving slowly to keep themselves stable.” – Becky (13:07)
• They typically rest 8–12 hours a day, mostly when it’s dark and quiet.

Memorable Quotes & Moments

• On fish lacking eyelids:
  • “So when they sleep during the day, usually wedged between rocks or coral reefs, their eyes appear to be wide open.” – Narrator (04:07)
• On dolphin rest:
  • “It might sound totally crazy, but when a whale or dolphin goes to sleep, only half their brain shuts down and only one eye closes.” – Narrator (06:15)
• On Jellyfish:
  • “No, I’m saying the jellyfish is a no-brainer because it has no brain.” – Becky (10:10)
• Octopus sleep:
  • “Octopuses have two kinds of sleep. Quiet and active. During quiet sleep, they lay motionless. During active sleep, they may change color and their eyes flicker around.” – Becky (12:54)

Notable Timestamps

• [00:45]: Introduction to animal sleep (humans, pets, land animals)
• [02:06]: Underwater adventure begins; moray eel encounter and eyelids question
• [03:34]: Eels are nocturnal; discussion on sleep patterns in fish
• [04:46]: Sharks and fish sleep myths debunked
• [05:24]: Parrotfish’s unusual bedtime routine
• [06:14]: Whale and dolphin sleep explained (unihemispheric sleep)
• [07:33]: Unihemispheric sleep defined; sleep habits of marine mammals
• [08:12]: Visit to the aquarium; meet marine biologist Becky
• [09:44–10:22]: Jellyfish facts – no-brainers, no central nervous system
• [11:22]: Experiments on jellyfish sleep and results
• [12:15]: More marine marvels: walruses, seahorses, otters, sea stars, octopuses
• [13:07]: Goldfish sleep patterns at home

Tone & Style

The episode is science-packed, silly, and accessible, filled with creative metaphors (like a parrotfish “sleeping bag” and walrus “pool floaties”), playful banter, and easy-to-understand explanations—making complex animal biology kid-friendly and fun!

Takeaways

• Fish and many aquatic animals don’t have eyelids—but they do sleep!
• Aquatic sleep comes in amazing forms: mucus cocoons, holding hands, sticking to rocks, and even sleeping with one eye open.
• Even jellyfish, despite lacking a brain, seem to need something like sleep!
• Animal sleep is as weird and wonderful as the creatures themselves.

Keep those curious questions coming and keep on smarting with “Who Smarted?”!