Secret Bay

Patches of the sand are hot. Water heated somewhere below the seabed jets up out of them, and on this dive that is ordinary scenery, something a guide swims past on the way to the next animal1. Mainit is Tagalog for hot. It is the name of the barangay on the beach, and it is why this site is also called Mainit Muck.

The slope is black volcanic sand, silt and rubble, and it runs about 150 metres straight out from the beach into Batangas Bay, dropping gently the whole way. You roll off into shallow water, get down onto the bottom and start hunting. The terrain does none of the work. There is no wall to follow and no structure to orient on, which is why the dive is easy and why almost nobody finds anything without a guide.

Operators split the slope into three sections and plan the dive around one of them, so it is worth asking which you are getting. The western end, next to Mainit, is nudibranch ground. The middle carries rocks and patches of seagrass, and that is where the whip-coral shrimp, the gobies and the seahorses live. East of that the sand goes bare, with sea pens standing in it and fire urchins carrying their zebra crabs and shrimp, and the eastern side is the section operators name for wunderpus and mimic octopus.

Most of the diving sits between about five and twenty-two metres and most of it is slow. Seventy minutes is a normal dive. Work down the slope instead of along it, though, and the sand runs out around twenty-seven metres, where coral outcroppings stand with black coral trees on them, polyps out and white, and longnose hawkfish darting through the branches2. Those are deep-water animals, and finding them at the foot of a muck slope is not what this site is sold for.

A marine scientist came here in 2009 expecting to waste a dive. He had been told it was the site the shop used for check-out dives, and he had heard the name before. "There's a Secret Bay divesite in almost every dive destination around the world," he wrote, and he took the briefing for local sales talk about an ordinary site. From the boat it did not help: a shack on the shore, one outrigger, nothing to look at. His own account closes that thought with a line. "How wrong was I!"3

Then he logged the next seventy-two minutes as they happened. A long-armed octopus at 9:02. A thorny seahorse at 9:12. An ornate ghost pipefish at 9:30, and at 9:37 a mototi octopus, the first he had ever seen, hiding in an old bottle and coming out to clean rocks away from its front door. A mimic octopus three minutes after that. A frogfish at 9:52, a blue-ringed octopus at 10:01, a jawfish at 10:08, a common seahorse at 10:11. Eight species of nudibranch, three shrimps, a couple of scorpionfish and garden eels on top of the list3. A sighting roughly every six minutes for an hour, and four species of octopus in one dive.

His verdict came at the end of it: "I rate Secret Bay as better than the muck dive sites of Lembeh & Wori Bay in Indonesia, better than Seraya Secrets in Bali, better than Lion Island in Papua New Guinea and even better than the Pipeline in Australia!"3

One diver, one morning, one dive. What makes it carry is the order he wrote it in, because the scepticism went down in print before the animals did. The site is still used for check-out dives, and both facts hold at once for the same reason: the diving is easy and the animals are hard to see. It was also the most popular muck site in Anilao as of late 2023, with the caveat the diver who said so attached to it, that currents shift and the animals shift with them season to season.

Six Pikachus on one dive. Thecacera pacifica is a small orange nudibranch that photographers named after the cartoon, and a visiting photographer counted six of them on a single dive here in both the silver-grey and the orange colour phase. The western end of the slope is where the nudibranchs concentrate, and eight species came off one seventy-two minute dive.

You will not find most of it yourself. The people who dive this slope every day know which bottle the octopus is living in, and the pace of a dive here is theirs, not yours. Tell them at the briefing what you are shooting and let them work ahead of you.

Everything worth photographing sits on silt and you will be working centimetres above it. One badly placed fin stroke takes the visibility away from every diver behind you, and it does not come back inside the dive. Hover the sand, do not settle on it, and get the buoyancy right before you start looking rather than while you are framing.

Set the expectations on water quality low and you will be fine. Ten metres of visibility is the usual figure here and it is a good day, not a bad one. The bay traps nutrients flowing out of Batangas Bay, which is precisely why the animals are here in these numbers, and it traps floating rubbish along with them. Compose around it.

The published depths for this bay disagree, and the gap is worth closing before you dive it. Almost everything happens between five and twenty-two metres, which is where the animals on this page were found. The outer slope has been dived to twenty-seven by a scientific field team, and the black coral is down there2. The shallows come up to about four metres at the top of the bay. An Open Water card covers the half of the site everyone actually comes for, and the page is graded Advanced because the deep end goes past eighteen metres and holds the one thing here that nobody else describes.

Nitrox is worth taking if the shop fills it. Dives run past seventy minutes, people do three or four a day, and a shallow site is exactly where that loading gets ignored.

The season here works backwards from the rest of Anilao. The main dive coast faces west into Balayan Bay and takes the southwest monsoon from around June to October, and when it is blown out the sheltered water is on the eastern side of the peninsula. This bay is on that side, facing Batangas Bay, and it is one of the few dives on this coast reachable by road as well as by boat. The trade comes in the other half of the year, because amihan, the northeast monsoon, is what chops this shore and stirs the bottom, and amihan is the settled season everywhere west of here.

Divers are asked to look and not touch, and the reason given locally is that rising diver numbers have thinned out how often some of the critters appear. Nothing on this slope needs handling to be seen.

One dated account belongs on this page. In 2017 a photographer was working the bottom here when a strong earthquake struck. A noise like cracking thunder, the sand shaking, silt lifting around the group, and a second shock hard enough that they went up to the boat, where the captain told them he had watched buildings swaying ashore1. This is a volcanic coast and the hot sand underneath you is the same story in a quieter form. It is one recorded morning, not a forecast.

Last, and it applies everywhere in this area. Nobody can show a recompression chamber working in Anilao. The closest one that anybody can evidence is in Metro Manila, about 140 kilometres away, and those two and a half to three hours of driving only start once you are ashore, after a boat leg of fifteen to thirty minutes. Secret Bay is one of the few dives here with a road to the beach, so that first leg can be the short one. Keep DAN Asia-Pacific to hand on +61 8 8212 9242, hold cover that pays for a chamber and the transfer, and check the boat has oxygen aboard.