20/06/2026
The answer is... Moon Fish! While most deep-sea creatures are slow, sluggish, and cold-blooded, this fish keeps its entire body core toasted to about 3°C to 6°C warmer than the freezing water around it.
How does it pull off this biological flex?
🏋️ It swims by rapidly flapping its pectoral fins like underwater bird wings. This constant workout acts as a massive internal engine, pumping out serious body heat.
🛡️ It has a specialized network of blood vessels in its gills called a rete mirabile. Warm blood leaving the body pre-heats the cold oxygenated blood coming in from the ocean before it can chill the fish's core.
🧥 Layers of fatty blubber wrap around its vital organs, keeping that hard-earned warmth locked in.
While its prey is slowed down by the icy deep-sea depths, the moonfish stays fast, sharp, and hyper-alert. We wonder if that is part of the reason why it’s so tasty! 😋