The Mystery of San Juan Island  

THE MYSTERY OF SAN JUAN ISLAND

30 July 2025 Feature | Surigao Historical Society | Local History

From Chapter VII of  'Surigao Across the Years' by Fernando A. Almeda Jr., D. Litt.

In this week’s deep dive into Surigao Across the Years, we turn to Chapter VII, San Juan, Intimation of Atlantis, which tells the story of one of the region’s most enduring mysteries, the vanished island of San Juan. Once mentioned in the journals of 17th-century English seafarers like Captain Charles Swan and William Dampier, the island has since disappeared from all modern maps. Was it claimed by nature’s unpredictable forces, or was it simply a mistake on old maps that turned into legend over time? Local Historian Dr. Almeda Jr. takes readers on a fascinating journey through archival records, seafaring tales, and geological theories as he pieces together the story of this elusive island. 

A CHARTED BUT LOST ISLAND
San Juan Island was once a familiar name in old maritime journals and colonial-era maps. English adventurers Captain Charles Swan and William Dampier, who sailed through Philippine waters in the late 1600s, both mentioned the island as a landmark during their voyages along the Pacific coast of Mindanao, near Siargao Island. These references show that, at the time, the island was seen as a real part of the seascape, something known and used by European sailors as they navigated these waters. 

THE EVIDENCE FROM MARITIME JOURNALS
Dr. Almeda builds much of this chapter on the journals of Swan and Dampier, an account of  Fr. Buzeta and Bravo, whose logs were among the earliest European documents to describe the Surigao coastline in detail. Both mentioned San Juan as if it were a fixed point, an observation that later found its way into European maps. The reliability of these sources adds weight to the mystery: 

Were they mistaken, or did they really encounter a landmass that has since vanished?

THEORIES: SUNKEN LAND OR CARTOGRAPHIC ERROR?
Dr. Almeda does not hold back when it comes to offering possible explanations. One theory looks at the volatile geology of Surigao. Sitting right along the Philippine Trench and within the Ring of Fire, the region is no stranger to earthquakes and volcanic activity. A powerful undersea quake, possibly triggered by a volcanic eruption, could have caused the island to collapse and slowly sink beneath the sea over the centuries.

Another theory leans toward something more human and less dramatic. In the 17th century, cartographers often worked with crude instruments and secondhand stories. It wasn’t unusual for mistakes to appear on their maps. What they thought was an island might have been nothing more than a cape, a cloud, or even a shadow on the horizon. Still, that one small mistake could have been copied and recopied in later maps until it became accepted as fact.

THE LARGER CONTEXT: INTRODUCING ENGLISH PRESENCE
While Chapter VII offers a quiet pause in the middle of stories about colonial struggles and missionary efforts, it also gently brings to light the often overlooked role of English navigators in Philippine history. These explorers were not colonizers, but they left their mark in other ways, through old maps, travel journals, and seafaring legends.

Dr. Almeda shows how England once tried to build a maritime trade relationship with the Sultanate of Maguindanao. But things didn’t end well for everyone. Captain Swan, one of the English adventurers, was eventually executed on the orders of the Sultan after a dispute, a stark reminder of how fragile such early encounters could be.

A PUZZLE THAT PERSISTS
Even with all the modern tools we now have in cartography and marine science, San Juan Island remains unconfirmed. It still hasn’t shown up in any recent studies or surveys. Historians and geographers continue to be intrigued by it, drawn to the mystery it holds.

Maybe it really did sink somewhere deep beneath the Philippine Trench, or maybe it was never there to begin with, just a trick of the eye or a sailor’s tale passed down through maps. Either way, its story lives on in the pages of Surigao Across the Years, a reminder that some mysteries are worth remembering, even if they’re never fully solved.

A HISTORICAL MYSTERY WORTH REMEMBERING
Dr. Almeda’s telling of the San Juan Island story reminds us that history isn’t just about wars, leaders, and big turning points. It’s also about the mysteries that live on the edges of what we know. We may never find the lost island, but because of stories like this, it still holds a place in Surigao’s cultural and historical memory.

It’s not the only mystery, either. There’s also the long-running debate between Butuan and Southern Leyte over the true location of Mazau, the island where the first Easter Sunday Mass in the Philippines was said to have taken place. Just like San Juan, it shows how some questions from the past remain alive, sparking curiosity and conversation even today.

THE LOST ISLAND OF SAN JUAN, FOUND AT LAST?

The order of disappearance of the island under three different names has been traced by Morton J. Netzorg as follows: St. Johanna, 1750, St. John, 1850, and St. Johannes, 1880.

In his work about San Juan, which he aptly called a “cartographer’s puzzle,” Netzorg opened his search for the mysterious island with a quotation from Lewis Carroll’s poem The Hunting of the Snark:

"What’s the good of Mercator’s North Poles and Equators?

"Tropics, Zones and Meridian Lines?"

So the Bellman would cry, and the crew would reply

"They are merely conventional signs!"

"Other maps are such shapes, with their island and capes!"

"But we’ve got our brave Captain to thank"

"So the crew would protest, 'that he’s bought us the best—a perfect and absolute blank!'"

What? Another mystery?

Note: It was only this year (2015), after almost 40 years since we wrote this chapter on the “lost” island of San Juan, that we finally came across a credible explanation and answer to the puzzle. The island of San Juan is actually not an island, but Cape San Agustin in Davao Oriental, according to Admiral James Burney.

ISLAND OF ST. JOHN/SAN JUAN

"near at hand, though we coasted within a league of the 'shore'."

This difference between the manuscript and printed journal cannot well be accounted for, the most remarkable particular of disagreement is in the latitude of the bay wherein they anchored, at this bay they had communication with the inhabitants, and learnt that the Mindanao City was to the westward, they could not prevail on any Mindanao man to pilot them, the next day, however, they weighed anchor, and sailed back southward, till they came to a part they supposed to be the SE end of Mindanao, and saw two small Islands about three leagues distant from it.

There is reason to believe that the two small islands here noticed were Sarangan and Candigar, according to which, Dampier's Island of St. John will be the land named Cape San Agustin in the present charts, and hence arises a doubt whether the land of Cape San Agustin is not an Island separate from Mindanao, Dampier's navigation between them does not appear to have been far enough to the northward to ascertain whether he was in a Strait or a Gulf.

The wind blew constant and fresh from the westward, and it took them till the 4th of July to get into a harbor or sound a few leagues to the NW from the two small Islands, this harbor or sound ran deep into the land, at the entrance it is only two miles across, but within it is three leagues wide, with seven fathoms depth, and there is good depth for shipping four or five leagues up, but with some rocky foul ground, on the east side of this Bay are small rivers and brooks of fresh water, the country on the west side was uncultivated land, woody, and well stocked with wild deer, which had been used to living there.

Ref, A Chronological History of the Discoveries in the South Sea Or Pacific Ocean (By James Burney) Vol 1, Chapt II p.243

Note: We have written at length, based on various references from other sources about the mystery of the island of St. John, which most cartographers say is actually the island of Siargao, this account of Admiral Burney saying that St. John is probably "Cape San Agustine" in Davao Oriental is the first credible explanation that in my view solves the mystery which I’ve been tracking over the last 40 or 50 years, (Dr. Almeda Jr.) 

THE VOYAGER AND THE VANISHED ISLAND

The expedition of William Dampier, as told in this chapter through the lens of the mysterious island of St. John or San Juan, played a key role in what would become the first English circumnavigation of the world. Dampier was part of that historic voyage, and he didn’t stop there. He would later sail around the globe two more times, completing three full circumnavigations, surpassing the earlier record held by Spanish explorers Sebastian del Cano and Gines de Mafra, who each circled the earth twice.

Dampier’s adventures didn’t just make history, they also shaped the future. As an explorer, writer, scientist, and keen observer of the natural world, his detailed notes and collections of plant life and animals helped lay the groundwork for later thinkers. Among them was Charles Darwin, whose theory of evolution was deeply influenced by the kind of global, observational exploration that Dampier helped pioneer.

THE MANY NAMES OF A LOST PLACE

The island of St. John, also known as San Juan, carries more than just a legend, it carries many names, shaped by the tongues of those who sailed near it. In French, it was called Isle of St. Jean/Île de Saint-Jean, in Portuguese, Isla de San Joare/Ilha de São João, in English, Island of St. John, and in Spanish, Isla de San Juan. Each name reflects the wide reach of explorers who once believed in its existence and marked it on their maps.

WHAT HISTORY OWES US

What this chapter quietly teaches is that one of history’s most important duties, whether local or national, is not to create mystery or leave it hanging unsolved. Its role is to investigate, to ask, to search for the truth, and to shed light on what has been forgotten or left unclear. The lost island of San Juan may still be missing from our maps, but thanks to stories like this, it remains very much a part of the journey toward understanding who we are and where we come from.

—Dr. Fernando A. Almeda Jr., 2025 

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