Stingless Jellyfish (Ubur-ubur tak menyengat)
Mastigias-type
In sheltered marine lakes, Mastigias-type jellyfish can be abundant and largely harmless to swimmers. They’re often called “stingless,” though some populations have very mild stinging cells; the experience is typically gentle, surreal, and slow-paced.
HabitatIsolated marine lakes and enclosed lagoons
DietPlankton plus symbiotic algae (zooxanthellae)
SizeUsually ~8–10 cm bell diameter
BehaviorSlow drifters; gather in sunlit water; daily movements
Where you might see it
At Lake Mariona (Jellyfish Lake) in the Togean Islands, where swimmers can float among dense groups of gentle jellyfish in calm, enclosed water.
How to spot it
You’ll see soft, amber “dots” pulsing just below the surface in still water. Enter slowly and let your eyes adjust then they appear everywhere.
Responsible Encounter Guidelines
- •Don’t touch or scoop jellyfish.
- •No fins (can injure them); float gently.
- •Avoid sunscreen oils in the lake; cover up instead.
- •No soap/shampoo before swimming.
- •Keep noise low; respect local rules.
Gallery
Conservation Status
Often not formally assessed; highly sensitive to pollution, temperature shifts, and human impact in enclosed lake ecosystems.