We are in the Lembeh Strait, the world’s capital of muck diving. And the question guests and students ask us more than almost any other is a fair one: what is muck diving, exactly?
Nobody’s first reaction to the word is a good one. Put ‘muck’ in front of ‘diving’ and most people picture something they would rather not swim in. When divers imagine diving, they think of clear blue water, coral and turtles. The reality of muck diving is close to the opposite of what the name suggests, and once people have tried it, a lot of them stop wanting to dive anything else.
Muck diving, defined
Collins Dictionary is no help at all. It gives ‘muck’ as moist manure; black earth containing decaying matter, used as fertiliser; mire or mud; anything unclean or degrading.
Here is the working definition from the water. Muck diving is diving over a soft bottom — sand, often black volcanic sand, plus silt, mud and rubble, sometimes with patches of coral. There is usually decomposing wood and vegetation in it, and often man-made debris too. All of that junk is shelter, and shelter is the whole reason the animals are there.
So the muck diving meaning that matters is not the dictionary one. It is a description of the seabed, and of the very particular cast of animals that seabed supports.
Where the term came from
Bob Halstead is generally credited with coining it in Milne Bay, Papua New Guinea, in the 1980s. It was the Lembeh Strait in the 1990s that made it famous. Muck diving is done in plenty of places now — elsewhere in Indonesia, in the Philippines, in Papua New Guinea — but for sheer range of species in a small area, Lembeh is still the benchmark everything else gets measured against.
Muck diving and macro diving are not the same thing
The two terms get used interchangeably and they should not be. Macro diving describes the photography: small subjects, a macro lens, and you can do it on a pristine coral reef hunting shrimps and nudibranchs. Muck diving describes the terrain you are diving over.
Most muck diving is macro diving. Not all macro diving is muck diving.
What actually lives on a black sand slope
The point of diving muck is that the animals living there are hard to find anywhere else. They have adapted to open sand with nothing to hide behind, so instead of hiding they pretend to be something else: a leaf, a stone, a strand of weed, a lump of sponge.
In Lembeh we see, on a regular basis rather than as a once-a-season event: frogfish including the hairy frogfish, ghost pipefish, nudibranchs by the hundred, stargazers buried with only their eyes showing, Ambon scorpionfish, dragonets, flying gurnards, seahorses, sea moths, pipefish and pipehorses. Then there are the cephalopods, which are the ones that tend to break people: mimic octopus, wonderpus, coconut octopus, mototi octopus, flamboyant cuttlefish, bobtail squid.
Somewhere in your first few dives you will surface saying ‘what on earth was that? I have never seen that before.’ That reaction is more or less the product.
It is nowhere near as drab as it looks
The sand may be black, but plenty of what sits on it is not. Nudibranchs come in eye-catching patterns and there seems to be an infinite number of them to try to identify. Flatworms ripple past in orange and pink. Peacock mantis shrimp earn their name. The flamboyant cuttlefish flashes pink, yellow and purple as it walks — it walks rather than swims — across the sand.
Add the ever-changing colours of the octopus and squid, and the black backdrop stops being a drawback. It is what makes everything else pop — which is a large part of why underwater photographers keep coming back.
Your first muck dive
On your first descent over the seemingly barren black sand you may quietly wonder what the point is. A few minutes in, the sand you thought was empty turns out to be full.
Finding the animals yourself is hard at the start. Some are tiny. Some do not look like animals at all. It takes an experienced eye, and this is where the guides earn their keep — ours have thousands of dives in this strait and there seems to be no limit to what they can spot. After a few dives your own eyes adjust, and you start finding the weird and the wonderful for yourself. That is the moment most people get hooked.
Buoyancy is most of the skill
Muck diving asks more of your buoyancy than reef diving does, for one simple reason: the silty bottom is a few centimetres below you and you are hovering over it, close to small and fragile animals.
One misplaced fin kick raises a sandstorm behind you. Waving your arms about does the same. You lose the animal, the visibility goes, and you make no friends among your dive buddies, particularly the ones holding cameras. A gentle frog kick and still hands solve most of it.
Slowly, slowly is the rule. Slow makes buoyancy easier to hold, and it gives you the time to actually look — which is the other half of why slow divers see more.
Why Lembeh Strait
The strait is a narrow channel between mainland Sulawesi and Lembeh Island. It is one of very few places in the world where the hairy frogfish, pygmy and thorny seahorses, mimic octopus, wonderpus and flamboyant cuttlefish are all regular sightings rather than a lifetime highlight.
Two Fish Divers Lembeh sits on a private beach in the middle of the strait, so some sites are five minutes away by boat in either direction. That means less time in transit and more time underwater. We dive a maximum of four divers to one guide, and up to four dives a day is possible — a morning pair, an afternoon or dusk dive, and night dives for mandarinfish and the nocturnal cast (Lembeh dive prices).
The strait dives year-round. Water sits between 26 and 30°C, the critters are resident rather than seasonal, and the calmest conditions are usually March to June and September to November.
Lembeh is not only sand, either. Some sites have small walls and slopes covered in soft coral, so a week here is not seven days of the same dive. And it is not the only place we find muck — there is good muck diving in Amed too, on the other side of Indonesia.
Is muck diving for you?
Three sorts of diver tend to fall for it, and none of them are specialists.
Critter hunters. Divers who turn up with a species list rather than a view in mind. Mimic octopus, hairy frogfish, blue-ringed octopus, flamboyant cuttlefish, pygmy seahorses, wonderpus, rhinopias — the species list reads like a marine biology wish list. Critter hunting is slow, deliberate diving: you cover very little ground and look very hard at all of it. You are not doing that alone, either — our guides have thousands of dives in this strait and are experts at spotting the critters.
Underwater photographers. Lembeh is close to a purpose-built studio. Cooperative subjects that sit still for your shot. Black sand backgrounds that make subjects pop. Multiple highlight species on a single dive. A macro lens is essential and external lighting is recommended. This is where portfolios are built.
Everyone else. No camera, no list — just divers who want to see animals they will not see anywhere else. Watching a mimic octopus change shape is worth the trip on its own.
What all three have in common is buoyancy rather than experience. Muck diving needs good buoyancy — you hover centimetres above the sand near small, fragile creatures, without touching down or kicking up silt. It is not about depth or current. It is about control. If you can hold good buoyancy without touching the bottom, you’re ready.
Which does assume some dives behind you and a degree of comfort in the water. If you have not dived for a few years, our centre in Amed or our resort on Bunaken Island is a gentler place to shake the rust off first — and Bunaken is only two hours from Lembeh, which is why our Walls & Muck Safari puts them back to back: three nights of muck diving in Lembeh, then four nights on Bunaken’s coral walls.
Frequently asked questions
What is muck diving?
Muck diving is scuba diving over a soft seabed — black volcanic sand, silt, mud and rubble — rather than over coral reef. The debris and sediment shelter animals that are hard to find anywhere else, which is why divers travel a long way to do it.
What does “muck” mean in muck diving?
It refers to the sediment on the bottom, not to anything dirty. The name comes from the look of the terrain — dark, silty and unpromising at first glance — and stuck, despite the diving itself being nothing like what the word suggests.
Is muck diving the same as macro diving?
No. Macro diving describes photographing small subjects and can be done on a coral reef. Muck diving describes the type of seabed. Most muck diving is macro diving, but not the other way round.
Where is the best muck diving in the world?
The Lembeh Strait in North Sulawesi, Indonesia is widely considered the capital of muck diving. The term was coined in Milne Bay, Papua New Guinea in the 1980s, but Lembeh made it famous in the 1990s and is still the reference point for species diversity.
Do I need to be an experienced diver to try muck diving?
No, but you need decent buoyancy control. Hovering close to a silty bottom without kicking it up is the core skill. If you are newly certified or have not dived recently, build the skill somewhere more forgiving first.
Originally written by Richard Becam, Dive Manager, Two Fish Divers Lembeh. Updated August 2026 with new photographs from the Lembeh Strait.
Want to see it for yourself? Get in touch and we will help you plan a trip to Lembeh, or read more about diving in Lembeh.
