Secret Bay

Secret Bay (also called Mainit Muck) is one of Anilao’s most productive muck dives — a shallow black-sand site with geothermally heated vents bubbling up through the sand, creating habitat for an exceptional density of cryptic critters and rewarding divers day and night.

Overview

Secret Bay is a shore-entry black-sand muck dive where geothermally heated water jets up from patches of hot sand — a noticeable and distinctive feature of the dive. The black volcanic sand continues from the beach directly into the water, sloping to a maximum of 21 meters. The combination of geothermal activity and muck substrate creates unusually diverse microhabitats across the site. Multiple independent sources confirm this is one of Anilao’s most productive critter dives, with sightings beginning as shallow as 5 meters.

Site Information

• Location: Mainit area, Anilao, Batangas, Philippines
• Entry Type: Shore entry
• Site Type: Muck dive
• Difficulty Level: Beginner
• Maximum Depth: 21 meters
• Typical Visibility: 10–20 meters
• Current: Generally mild
• Best Time: October to May; excellent year-round including night dives

Marine Life

Sources consistently confirm the following species at Secret Bay: thorny seahorses, ghost pipefish, frogfish (small specimens), wonderpus octopus, Coleman shrimp, nudibranchs, mantis shrimp, oriental sea robins, pipefish, demon stingers (a stonefish relative), dragonets, snake eels, and Ambon scorpionfish. Squid and cuttlefish come into the shallows at night and are regularly encountered on evening dives. Blue-ringed octopus are also reported at this site. Note: “broadclub cuttlefish” as a specific species was not confirmed in site-specific sources — sources refer to cuttlefish and squid generally in the night-dive context.

Dive Profile

Enter from shore and descend onto the black sand slope, which begins producing critters almost immediately at 5 meters. Work methodically along the slope, checking every sand patch for mantis shrimp burrows and scanning the open sand for seahorses, pipefish, and dragonets. The geothermal vents are warm to the touch — feel the water above active vent patches. The productive range extends to approximately 15 meters, with the maximum depth at 21 meters. This is an excellent night dive site with different species active after dark.

Entry and Exit

Shore entry from the Mainit area beach. The black sand entry is straightforward. Exit at the same point. Shore access makes this an easy site for multiple dives at any time of day, including night.

Tips and Recommendations

• Touch the sand near bubbling vent patches to feel the geothermal warmth — a unique sensory feature of this site
• Night dives are particularly productive; squid and cuttlefish come into the shallows after dark
• Move slowly and scan systematically — most critters rely on camouflage against the dark sand
• A focus light or torch is useful even during daytime dives to illuminate burrows and dark patches

Safety Considerations

Shallow and generally mild conditions make this a safe site for beginners. Demon stingers are venomous — never place hands or knees on the sand without looking first. Night dives should be conducted with a good primary light and backup. Shore entry means no boat traffic above, but notify your resort of planned dive times especially for night dives.

Sources: DivePlanIt – Secret Bay, EAZY Traveler – Secret Bay Anilao, Underwater Photography Guide – Anilao Diving. Last updated 2026-06-25.