I was in Manila for 2 days in Feb. 2013. The closest good diving is a few hours South on the Anilao peninsula near the city of Batangas. I've heard that it's not recommended to dive here on a day trip from Manila since most of your day would be spent travelling. I figured I'd get there in the evening, spend the night and dive the next day before heading back to Manila in the evening of the second day. The first leg of the trip was 2.5-hours on a coach bus to Batangas. From there, I was naive enough to try and take a taxi to Anilao. This is the most expensive option, but I figured it would be the quickest way to get there. Unfortunately, I later discovered that the taxi drivers here mysteriously don't know how to get anywhere, they can't read maps and your journey ends up taking several times longer than you expect. I later learned that the "trikes" (motorcycles with covered sidecars) and jeepneys (public transit truck/buses) are much quicker, more reliable and about 1/20th of the cost. Anyway, I finally arrived in Anilao hours later in the middle of the night and checked in to the closest dive resort (Monte Carlo Dive Resort). The next day I joined a group of Korean divers for 3 dives. The dives we did were "Cathedral" (two pinnacles next to each other going down to about 80 feet deep on the seaward side), Eagle Point (a slope of coral down to 60-80 feet or so and "Twin Rocks"(a popular, shallow, shore-diveable house reef for the adjacent resorts). So far, I think this is the best tropical diving I've ever done. There was the biggest variety of hard and soft corals that I've ever seen. Visibility was about 100 feet on the first two deeper dives and 30-50' on the shallow last dive. The water temperature was 26 degrees.
I'd agree that only doing one day of diving here is pretty hectic and tiring with all the travel, but I'd do it again.