Spiny reef vacuums. Eat algae continuously — and the long-spined ones have venomous tips.
Sea urchins are echinoderms (cousins of sea stars and crinoids) that graze algae continuously, suppressing algal growth that would otherwise smother coral. Their loss to disease in the Caribbean in the 1980s drove a regional reef collapse — they're keystone species.
Long-spined sea urchins (Diadema setosum) have venomous spines that can break off in skin — painful, never lethal, but a memorable accident. Slate-pencil urchins, fire urchins and crown urchins all have distinct safety profiles.
Common at every Indo-Pacific destination. Look for the symbiotic urchin shrimp and zebra crabs that live on the spines of some species — a macro reward.
Tap a month to highlight it across destinations, or hover any cell for details.
18 destinations across Goa, Andamans, SE Asia, Indian Ocean, Arabian Gulf, East Africa — peak seasons vary by location, so plan your trip around the right destination AND the right month.
Tier 1Sea Urchins here: Jan–May, Oct–Dec · 12 sites
Tier 2Sea Urchins here: Jan–Apr, Dec · 30 sites
Tier 1Sea Urchins here: Apr–Nov · 35 sites
Tier 1Sea Urchins here: Feb–Sep · 25 sites
Tier 1Sea Urchins here: Jan–Apr, Nov–Dec · 40 sites
Tier 2Sea Urchins here: Jan–Apr, Nov–Dec · 15 sites
Tier 2Sea Urchins here: Apr–Nov · 25 sites
Tier 2Sea Urchins here: Jan–May, Dec · 30 sites
Tier 2Sea Urchins here: Jan–Apr, Oct–Dec · 25 sites
Tier 2Sea Urchins here: Jan–Apr, Sep–Dec · 20 sites
Tier 4Coming soonSea Urchins here: Jan–May, Oct–Dec · 15 sites
Tier 3Sea Urchins here: Apr–Nov · 40 sites
Tier 3Coming soonSea Urchins here: Jan–Feb, Jul–Dec · 22 sites
Tier 3Coming soonSea Urchins here: Apr–Oct · 12 sites
Tier 3Coming soonSea Urchins here: Jan–May, Nov–Dec · 20 sites
Tier 3Coming soonSea Urchins here: Mar–Oct · 18 sites
Tier 4Coming soonSea Urchins here: Apr–May, Sep–Nov · 30 sites
Tier 4Coming soonSea Urchins here: Jan–Apr, Oct–Dec · 50 sites
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