1. When dolphins sleep they are only resting half of their brain at a time and have one eye open to watch for predators.
2. An octopus’s blood is blue.
3. A shrimp’s heart is in its head.  
4. Sharks have six senses. 
5. Cyanobacteria found in fossils are estimated to be 3.5 billion years old.
6. Sea pigs are animals that live deep in the ocean and disintegrate if there is not enough water pressure.

Cites:

https://allthatsinteresting.com/

https://www.nhm.ac.uk/

https://ucmp.berkeley.edu/

https://awionline.org/