I was there in Mar-April for 6D/5N dives, dived with Borneo Divers who also owned the only chambers in that area.
It was worth the effort of travelling there. The water vis is 40 - 50m !!! So rich are the wall corals, trutles and whitetips, that I am happy just being stationary in the waters to let the fishes pass me. Your bouyancy skills will sharply improve there too. With a 2000m depth, I rather practise hard.
We managed to talk our way out to do the turtle tomb cave dive. A senior instructor took our group (all advance divers), only after day 3, after being observed by the resort director and other senior staff. There are bones of dophines, trutles, and caves formations. (I have never been in one).
You can arrange boat trip to Mabu, Kapalai island for a small fee. I dived of the surrounding of a retired oil rig off Mabu island. Muck diving, vis dropped to 10 - 15 m, but lots of microlife. A real test of my patience and observation skills - graden eels, ribbon moray etc etc....
At night, the night dive off sipadan (a shore dive) offers a lot of interesting stuff too. HUGE bumpheads Zzzz away, while you go up close and pat them....
One can hit up to 4 -5 dives daily, if your dive profile allows. Well, we did about that daily.... "while we are still young and energitic". It is unlimited shore dives.... That means that our DC are on us all the time. Realise how bulky Aladin Pro are....
I dun have the u/w pix to share but here are some party stuff....
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Sipadan Pix
...... I will return