The 1 night layover in Tawau from JB isn't going to work because you have to board that LOB on a Wednesday. So you'd want to stay in Tawau for 1 night (on Tue) but there are NO FLIGHTS from JB to Tawau on Tuesday so you would have to go on Monday. Which means you gotta spend 2 nights in Tawau (Mon and Tue) before you can even start the LOB. Similar situation on the way back because JB to Tawau and Tawau to JB flights aren't daily. So you end up wasting 4 nights as layover. Think it's quite obvious to all that this sort of itin won't work.

Never mind. Thanks for all your efforts.

To obtain the good things in life, more effort is needed. Looks like an 8+ day vacation is needed to dive Sipadan from the Celebes LOB. It's good information for making plans for future diving trips. If not this year, then maybe next year?

I did my sipandan dive 2 yrs ago, not sure whether the information is still useful.
I depart from senai in the morning, reach KotaKinabula using airasia, change flight using Msia airline reach Tawau on tat same day ard 4, stay there for 1 nite. Hope this helps.

sipadan got LOB meh...the sites are pretty standard and not innumerable
[i'm biased towards Seaventures due to great personal experience with them - it's a unique rig to stay on]
keep an eye on the security situation there too..

Yep, that's the one. I ended up not going on that trip because I just couldn't make it work with the Celebes itin. Heng ah, it turned out a policeman got killed and another got kidnapped the very week I had planned to go.

So sorry chuanfatt, couldn't help in this case. It will be pretty manageable if you aren't looking to do the LOB as others have said.