Sombrero Island

Stiff surge meets you the moment you are under, pushing and pulling until the descent gets you down to the reef. Then the island does the work. Wide gullies and coral heads big enough to hide behind run through the rim, and they are cover from the flow, which is the whole technique here: get down, get behind something, and work the ground.

The reef is a hat brim. It runs north to south underwater all the way around the island, and one circuit takes in valleys, pillars, wall and flat ground without repeating itself. An instructor who dived it came up saying she had seen a fraction of what is there. It is more site than one tank covers.

What carpets it is Tubastraea, the cup corals people call sun corals, yellow polyps on pink bodies laid across the reef terrain. Current is what feeds them, and it brings in the fish that feed in it: clouds of anthias holding station over the rim, small barracuda off the edge, yellow snappers through the gullies, trevally and jacks moving above the lot. Cleaner wrasse work their stations. Crinoids sit on everything.

Most of the dive happens shallow. The top few metres carry the thickest hard coral on the reef, and that is where divers settle once the descent is behind them. The wall is the other half and the half to watch, because it falls away below anything the dive uses and gives you no floor to measure yourself against.

Sombrero sits at the western end of the Verde Island Passage, and this is the point where the passage's divided waterways rejoin and combine with the tidal flow of Balayan Bay. Several current lines converge over one reef. At full and new moon they run hard. That is a physical account of a site most descriptions handle with an adjective, and it explains both halves of the island at once: the current that feeds the cup coral and the fans is the current that takes divers off the reef.

The reefs here were recommended as a national marine park in 1982, alongside Sepoc Point and Layag-Layag, because the three are one reef complex1. Nothing followed. The recommendation was never acted on by the national government, and the island is still an unprotected reef with fishing pressure on it, a few kilometres from three no-fishing sanctuaries that were declared by ordinance in 1991.

What the monitoring measured since then reads in pairs. A severe storm in 1988 flattened the shallow reef, and live hard coral there climbed steadily afterwards to 74.0 percent by 2011, one of the highest shallow figures anywhere in the monitored series. Deeper, at seven to eight metres, hard coral went from 31.3 to 38.9 percent across the last six years of that series1. The fish went the other way over the same six years. Density across all reef fish dropped from 8,323 to 3,369 individuals per 500 square metres, and species diversity from 42 to 35, both significant drops, with continued fishing pressure in the area named as the likely cause1.

Twenty-three years of measured coral regrowth, and a fish community more than halved in six. One reef, no line on a chart around any of it.

There is no lens decision on this island. Wide angle is the dive: the rim, the gullies, the cup coral, and the anthias holding over all of it in the flow. Divers who shoot here describe it as swimming through a magazine cover.

Go in the morning, and this is the one piece of local knowledge worth planning around. Divers are told that wave action and current tend to be strongest at Sombrero in the afternoon, and boats that want the island leave early on that. Pair it with a neap tide and you get the two things the site withholds together, stillness and the clarity that comes of being offshore and flushed.

Light is the other half of it. Sun through shallow water onto a current-swept rim is what the good frames here are made of, and it is why the shallow reef gets the tank and the wall does not. The water here works for you, which is not this coast's habit: eighteen metres was measured on an October dive, the top of the local band.

Shooting in flow costs you position before it costs you anything else. The gullies and coral heads are the working answer. Get into their lee, let the subject come across the frame, and do not chase anything over open reef with the current behind you.

Watch the moon and watch the clock. Full and new moon are the named windows for the strongest converging current lines, and afternoons here are reported worse than mornings, so a shop that knows the island runs it early and on a neap.

Carry an SMB and expect to come up on it. This is the one reef in the group with no anchor buoys. Reef monitoring recorded that the area would benefit from having them in place1, and a first-hand account has a boat dropping anchor here instead. Arthur's Rock, Twin Rocks and Cathedral Rock all have buoys in and boats using them, and that habit does not travel across the strait. Deploy before you leave the reef, and take the ascent as yours to manage with boats working somewhere above you.

Settle the depth before the descent. The dive runs from about 5 m on the rim to 30 on the wall, with most of it between 5 and 25, and the reef does not stop where the dive does. One instructor's warning about this exact site is worth carrying: it extends well beyond recreational limits, and it is easy to forget how deep you actually are. There is no sand to arrive at and no break in the wall to mark the crossing.

Have a second site. Divers record wanting to dive Sombrero and being weathered off, one of them on two separate trips, and one group waited days for typhoon swell to drop before the island opened. From June to October the current here is described as stronger and not suitable for beginners. You take this island on the day it gives you.

Last, the leg nobody plans for. No chamber in Anilao is confirmed to be in service. The closest one with evidence behind it sits in Metro Manila, about 140 kilometres away down a road that runs two and a half to three hours, and a diver reaches that road only after fifteen to thirty minutes in a banca. Sombrero adds roughly twenty more, because from the Tingloy side the Maricaban Strait crossing goes first. So the longest chain on this coast belongs to the site with the strongest current, the deepest profile and no line to ascend on. Buy cover that pays for a chamber and an evacuation, ask whether the banca has oxygen aboard, and put the DAN Asia-Pacific number somewhere you can find it under pressure: +61 8 8212 9242.