Clownfish in their Host Anemone

Two bright orange anemonefish (Amphiprion ocellaris) poke their heads between anemone tentacles. Anemonefish are able to swim amongst the stinging tentacles without getting stung — but no one knows exactly sure how. One dominant theory explains that they have a protective slime coating their bodies. However, anemonefish are not born with this protective slime and scientists don't know how they develop it.

Two bright orange anemonefish poke their heads between anemone tentacles.
Credit: 

Flickr user Jenny Huang (JennyHuang)/EOL