Southwest of Manila, the snorkeling off Dimakya Island is well known it's dugongs, which are a relative of manaties. The dugong regularly feed on the seagrass off the island. When snorkeling off Dimakya Island, you will also encounter manta rays, green sea turtles and stingrays.
Tip - While snorkeling off Dimakya Island, make sure to use a diver down flag since the boaters tend to drive fast and be unaware of snorkelers in the water.
Overall, Dimakya Island is the 7th most popular snorkel dive spot of all 12 snorkeling dives in Philippines.