Across the Hilutangan Channel from Mactan Island, is Olango Island. There are three sites here that are worth the effort to see.
At Mabini Point on the northern tip of the island, diving to the depths will give you the best chance of seeing large pelagics - there is very little of interest in the shallower areas. Descending to around 35m at the drop-off, you will almost certainly encounter sharks, including hammerheads and the occasional whale shark. Currents are strong and unpredictable, so this is a dive for the experienced only.
Off the northwestern coast is Baring. Again there is little of note in the shallows, so descend to 30m and see whitetip and grey reef sharks, tuna, barracuda, snappers and jacks. Also worth checking out are a number of caves at 35m - you never know what you'll find inside.
Slightly further south is Santa Rosa. The dive starts with a sandy bottom covered in soft corals, leading to a drop-off at 15m, descending to 50m. There is a good variety of reef fish in the shallows here, while further down you'll see fusiliers, catfish, jacks, snappers and sweetlips, among others.