What the diving is like
The Lembeh Strait is a channel about sixteen kilometres long and between one and two kilometres wide, running between the mainland of North Sulawesi and the island of Lembeh. Both shores shelve into fine black volcanic sand, and it is the sand the destination is known for. A typical site is an even slope with very little relief: dark sand and silt, a weed patch, a stand of whip coral, a tyre, a length of rope. The animals are on and around that sparse structure rather than spread across the open bottom, which is why the diving is slow. Fifty minutes often covers a few tens of metres of ground, and much of that time is spent stationary while one patch is worked over. It suits photographers and people who like looking closely; it is not scenic diving and it does not reward covering distance. The strait is not all sand. Of the named sites below, about a third are black sand and the rest are coral, mixed rubble and coral, a few walls, two of white sand and one wreck. The channel is narrow and steep-sided, so boat rides between sites are short and the water inside it is sheltered in most weather. Current runs with the tide and strengthens on the flood.
The shape of a day
Three dives in a day is the usual shape, with a night dive for anyone who wants one. Boat rides are measured in minutes rather than hours, so the interval between dives is spent ashore rather than under way. The diving is arranged around spotting: small groups, long stops, and a guide who will stay with one animal while the rest of the group is somewhere else. Night dives are shallow, most of them inside fifteen metres. Days out of the strait are a different kind of diving again — the outer, eastern side of the island, or the reefs off the islands to the north — and both mean a longer crossing and wide angle rather than macro.
Getting there
Sam Ratulangi at Manado is the airport, about an hour from the strait by road, with a short boat crossing on top of that to reach the island shore. Non-stop international flights are limited to Singapore and Guangzhou and do not run every day of the week; most other routings come through Jakarta, Makassar, Surabaya or Denpasar and finish with a domestic leg into Manado. That domestic leg is where the baggage allowance gets tight, which matters with camera equipment.
When to come
Diving continues all year. The southeast monsoon, roughly June to October, brings cooler, nutrient-rich water into the shallows on a coastal upwelling, and it is the busier half of the year. The northwest monsoon from December to April is the wet one, and visibility in the strait often improves rather than deteriorates through it, with lighter winds making the exposed sites outside the channel more reliable. May and November are transitions.
Fees and what is not included
What is charged for diving in the strait is a local conservation or harbour levy rather than a national park fee. It is collected locally, in cash, and the amount changes, so it is worth asking what it currently is rather than reading a figure here. The reef parks nearer Manado charge their own daily entry and diving fees, paid on the day.