I've only dove in Cebu personally, but I can tell you that it is definitely up there in experiences.
I'm going back to Cebu next week for a month of diving and adventure. I've lost count on how many times i've gone there diving.
Fly into Cebu airport on mactan island, get a hotel at one of the resorts along the East cost of mactan and you can either shore dive or there are numerous boat dives to the sanctuaries that are at most 15 minutes by boat
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his is a link to a map at KI marine, for all the places within a couple minutes that you can dive. KI is a pretty local place and not affiliated with any resorts. Its inexpensive and gets the job done, just dont expect VIP treatment or top of the line equipment. its good rentals, just not brand new. If you want to be more comfortable, all the resorts offer diving, though at first world prices.
I dive there months at a time, there is enough just at mactan to keep you busy for a couple months for sure.
I like getting on a boat and trolling up and down the cost of mactan. all the dive sites there can be dove from shore, but you have to drive to each point. Grab a boat and you can just wander up and down the shore, diving wherever you fancy.
Kontiki house reef has a HUGE school of sardines and another of some other small fish. That schools been there for at least 2 years and there is a good sized group of predator fish that seem to heard them around and grab one when they're hungry. If you're around the school when the preditors jump them, then the school will rush you and you'll have a huge school swarming all around you for about 5 minutes straight. Theres a barricuda about a meter and a half wandering there too. visibility is about 3m here and the diving is between 5-15m with an infinitely deep wall after the 15m I'm not sure exactly how deep it goes, but its deeper than we can do. This is a busy diving area, but worth it just the same.
Maribago cave is more of a cavern that turns into a cave. if you start a dive here you can wander down about 30m to the mouth of the cavern, floor at 40m so stay high, you can pop into its mouth and go back up to about 25m after entering. it does go deep, but unless your set up for caving, just wander into the mouth and take a look around.
North of mactan, up to malapasqua is some shark diving, its worth a look, but its an overnight trip typically, then theres oslob, whale shark diving there, also a day trip, you can stay at the granada botique beach resort, bring some tanks for the resort because this is probablly the nicest diving on the island, right off the beach at the resort. (the owner is a british fella who's been diving cebu for about 30 some odd years, i think he has a compressor, but bring your own tanks anyway)
Dolfins, sea turtles and the odd shark at Moalboal on the other side of cebu island. Moalboal is kindof like mactan, the whole shoreline there is good.
Pescedore island is also a boat ride off moalboal and is very nice.