Sea anemones (like giant green anemones) naturally retract and tuck in their tentacles when the tide is low, the sun is strong, or exposure to air increases-this helps them reduce water loss, shield delicate parts, and protect their symbiotic algae.

When touched or disturbed-even gently-they contract quickly and squirt out water from their body cavity as a defensive reflex, allowing them to shrink, tighten their grip on the substrate, and avoid damage or drying out. (text copied from the og post)