Secret Bay

Secret Bay is a muck-diving site on a long, gently sloping sandy bottom located at the tip of the Calumpan Peninsula in Anilao, Philippines, where it traps nutrients flowing in from Batangas Bay. The slope runs approximately 150 metres straight out into the bay, reaching depths of 10–22 m, and can be divided into three zones: a western area bordering Mainit, a middle section of rocks and seagrass, and an eastern/central stretch of barren sandy bottom with occasional rocks, sea pens, and fire urchins. It is one of the most photographed macro sites in the Philippines and a site that helped establish Anilao's reputation among underwater photographers.

The three zones each hold distinct communities. The western area is the realm of nudibranchs, particularly Chromodoris and Flabellina species. The middle section hides whip coral shrimp, xeno crabs, gobies, and seahorses among rocks and seagrass. The eastern/central sandy slope hosts sea pens and fire urchins carrying zebra crabs and shrimp, while the eastern side is specifically known for wunderpus and mimic octopus, both of which are reported to interact with divers for the length of an entire dive. Additional regulars across the site include coconut octopus, Rhinopias in various species, flamboyant cuttlefish, common cuttlefish, bigfin reef squid, scorpionfish, lionfish, hairy and painted frogfish, shrimp gobies, snake eels, and the nudibranch Costasiella kuroshimae. Increasing diver numbers have reduced sighting frequency of some species, and a no-touch approach is strongly encouraged.

Conditions are generally beginner-friendly, with light current, water temperature between 27–30 °C, and visibility typically around 10 m. The site can become a little rough during the northeast monsoon (Amihan) season, which may stir up the sandy bottom, though the area remains productive year-round. Nitrox is recommended for extended bottom time on the shallow-to-mid-depth slope.