A great resource for divers in N Sulawesi is this website:
Keep following the linked pages as there is a ton of information about the islands from Sangihe to Bitung, including Manado.
Another dive information resource I recommend is Wannadive.net. They now have an app for your smartphone with all the dive site info on a map. They had all the dive waypoints in Lembeh and Bunaken (and all the ones in Palau, too).
If you have your own equipment you CAN dive Lembeh Strait on your own. There are two or three bays on the north/west side of the strait that have good sand plateaus to anchor in with the big boat, and from there, the dive sites are easily within dinghy distance. (Check this one: 01 29.46N / 125 14.25 E). Watch where the dive boats go. In spring 2017, there was an Eco-Divers boat anchored off the south side of Serena Besar that would fill tanks for $3 a fill, so getting fills when anchored there is easy.
We ultimately opted to dive with Bastianos Dive Resort, as recommended by our friends on s/v Sirius. They had great guides and we got a package of dives, so the dives only cost about $35 USD per dive (with our own equipment). We got so much more out of a guided dive than trying to do it on our own out of our dinghy. So many times our guide pointed out something that looked like harbor trash only to find it’s a rare/weird fish/invertebrate. We photographed a ton of new-to-us creatures in the 3 days of diving we did with Bastianos.
If you’re new to “muck diving” I’d definitely do at least one dive day with a dive operation. That said, diving in Lembeh isn’t for everyone. If you’re looking for blue water or coral, go to Bunaken instead, on the other side of the peninsula. But I’d definitely recommend a day or two of diving in Lembeh for any diver. The creatures are amazing.
As a 10th Wedding Anniversary present to ourselves, we had Bastianos arrange a visit for us to dive at Bastianos Bunaken. We got the transfer to and from Bastianos Lembeh to Bastianos Bunaken, 3 nights in a superior a/c room on the water, all meals, and 7 dives for two of us for around $1,500 USD. It was a great short getaway for us. Bunaken is the exact opposite of Lembeh…big coral walls, lots of (small) fish (some big), turtles, etc. We enjoyed diving both places equally, for different reasons.
Photos to follow soon.