Hiya, yes we went! It was very enjoyable. here is the review I posted on another thread
We booked Maratua Paradise resort as we had read some real negative stuff about Sangalaki. Then we saw a review written on Tripadviser about it and were horrified that maybe we had a made a huge mistake, but not so. Maratua Paradise may not be the best resort we have been to in Indonesia (and we are comparing with around 20) but it certainly isn't as awful as the other writer says. The resort organises everything from your arrival at Balikpapan airport to return. This involves a flight to Berau, a taxi to the boat and then 2.5 hours on a speed boat out to the island. The system was faultless. All the staff and crew friendly and helpful. OK, the boat was a little shabby but it was safe. The bungalows at the resort were huge and airy, air-con, fan, fridge, comfy bed. The dive centre again was pretty good, all the crew were charming and helpful, and the system well run. Food at the resort is far better than we thought, mostly fish or seafood, chicken once or twice but lots of vegetables and fruit, snacks free and available all day. Beer and soft drink prices were reasonable, much cheaper than in Manado where we spent our last trip.
The diving here is pretty good too. Sadly the corals are not in great condition but this is a mixture of natural and man-made causes. The water is too hot at 86 degrees and the corals are staring to bleach in some of the shallow areas. But the marine life is great - turtles everywhere, thresher sharks on the house reef and the dive at the Channel is outstanding for schools of big fish. We also dived on Kakaban, and both wall dives there were stunning, The jelly lake was good, not as good as Palau's but great all the same.
So that just leaves Sangalaki. Boy... were we disappointed. Bleached coral, Crown of thorns everywhere. We did 6 dives and no mantas. Over a 10 day trip, Maratua took a different group to Sangalaki almost every day and only one group got to see the mantas and only once. Loads of fishermen there too.
We really loved this area, great variety of diving but I wouldn't go just to see the mantas which was what we hoped. Maybe someone else has some more info on them, perhaps this is seasonal?
** Some extra info for you... I hear that the mantas can be seasonal so I guess we were just unlucky with the month. October. Nabucco dive on the east side of the island and Maratua on the west mostly so if you went again you would get different dives I think. Also, if you do go to Maratua, make sure you get a water bungalow. The beach ones were similar but lovely being over the water.