Hi Giovanni :) I dove with Scuba Junkie guys and stayed on Mabul Island, it was a very good experience, we were lucky enough to even spot a whale shark. Sure Sipadan was a lifetime experience. Here is my video from that trip https://www.youtube.com/watch?v=GeAPubpGiGo I don't recommend staying in Semporna even though it is much cheaper as this town is very dirty and SJ hotel there leaves much to be desired, while the one on Mabul was great.