Tiny, colourful, and often overlooked by non-divers, nudibranchs are the ocean’s weirdest little show-offs. These sea slugs may not look like much at first glance, but once you start spotting them, it’s hard to stop. Whether you’re a macro photographer, a critter nerd, or just someone who likes finding the ocean’s stranger side, nudis are pure treasure.
What Exactly Is a Nudibranch?
“Nudibranch” comes from the Latin for “naked gills” — they’re soft-bodied molluscs with exposed gills on their backs. They’re basically snails without shells, but way more flamboyant. There are over 3,000 species worldwide, ranging from tiny pinpricks to a good 60 cm long (though most are small enough to miss if you’re not paying attention).
Why Are They So Colourful?
All those neon stripes, dots, and patterns aren’t just for our cameras. Nudibranchs use colour to:
- Warn predators that they taste awful (or worse, are toxic).
- Camouflage against coral, sponges, or algae.
- Mimicry — some nudis copy the look of poisonous species for protection.
So yes, they’re as smart as they are photogenic.
What Do They Eat?
Nudibranchs aren’t picky eaters, but they do specialise. Depending on the species, they might feed on sponges, coral, hydroids, or even other nudis. Some can absorb stinging cells from their prey and reuse them for their own defence — a pretty genius move for a soft, shell-less slug.
Where Can You Spot Them?
They’re found worldwide, but tropical reefs are nudibranch central. The Philippines, Indonesia, and Papua New Guinea are especially famous for them. The trick is slowing down: look closely at sponges, soft corals, rubble, and sandy patches. Night dives can also be great for spotting species that hide in the day.
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Why Divers Love Them
- Photogenic: Bright colours, wild patterns, and plenty of variety.
- Accessible: You don’t need to go deep — many species live in shallow reefs.
- Challenging to Find: Makes spotting them feel like a win.
Macro lovers especially can spend entire dives happily focused on nudis while everyone else swims past.
Tips for Spotting Nudibranchs
- Slow down your dive — nudis don’t move fast, so patience pays.
- Check unusual surfaces: sponge walls, coral heads, algae, or under ledges.
- Don’t touch — they’re delicate, and many have toxins you don’t want to mess with.
- Bring a torch or macro lens if you’re into photography — their colours pop with extra light. (A torch like the OrcaTorch ZD710 is a versatile solution — its zoomable beam works brilliantly as your main dive torch, and when switched to a more flooded light, it doubles up nicely for photography. Perfect for when you want to balance exploring with a minimal set up and capturing those tiny, colourful details.)
If you’re a keen underwater photographer, nudibranchs make perfect subjects thanks to their slow pace and striking looks. Check out Mike’s Dive Cameras for a full range of macro lenses and strobes to help you capture every detail. For those more on the go — or on a tighter budget — our SeaLife phone case might be just what you need. It makes the most of your existing phone camera, which these days are excellent and often come with surprisingly strong macro features.
Nudibranchs may not be the biggest or flashiest animals in the sea, but once you start noticing them, you’ll realise just how much life hides in plain sight. From bold colours to bizarre survival tricks, these little sea slugs prove that small can be spectacular.
