Second Thomas Shoal

Also known as: Ayungin Shoal (Philippine name) · Buhanginan ng Ayungin (Filipino) · Rén'ài Jiāo / 仁爱礁 (Chinese) · Bãi Cỏ Mây (Vietnamese) · Second Thomas Shoal (English, after Captain Thomas Gilbert of the Charlotte) · Thomas Shoal Second (older gazetteer rendering)

Places

Definition

Second Thomas Shoal, known in the Philippines as Ayungin Shoal (Filipino: Buhanginan ng Ayungin, “sandbank of silver perch”), in China as Rén’ài Jiāo, and in Vietnam as Bãi Cỏ Mây, is a submerged coral atoll in the northeastern Spratly Islands of the South China Sea, lying about 105 nautical miles (194 kilometers) west of the Philippine island of Palawan. A tear-drop shaped reef roughly 11 nautical miles long from north to south, it fringes a lagoon with depths of up to 27 meters that is accessible to small boats from the east; drying reef patches lie east and west of the rim. The shoal is claimed by China, the Philippines, Taiwan, and Vietnam, and takes its English name from Thomas Gilbert, captain of the Charlotte, for whom several nearby shoals are also named. (Wikipedia — Second Thomas Shoal)

The reef has been occupied since 1999 by a small Philippine Marine garrison aboard the deliberately grounded landing ship BRP Sierra Madre, which the Philippine Navy periodically resupplies by sea. In the arbitration instituted by the Philippines under Annex VII of the United Nations Convention on the Law of the Sea, the tribunal held in its 12 July 2016 award that “Second Thomas Shoal is a low-tide elevation located within the exclusive economic zone of the Philippines,” that such features “generate no entitlement to a territorial sea, exclusive economic zone or continental shelf” and are not capable of appropriation, and that Mischief Reef and Second Thomas Shoal “are part of the exclusive economic zone and continental shelf of the Philippines.” China, which rejects the award, maintains that the shoal falls within its own claims. (Wikipedia — Second Thomas Shoal, 2016 Annex VII Award (RIAA))

Identities

Source Type	Identity
Wikipedia	Second Thomas Shoal
Wikidata	Second Thomas Shoal (Q6855008)
DBpedia	Second_Thomas_Shoal
ProductOntology	N/A
Wiktionary	shoal
Library of Congress Subject Headings (LCSH)	South China Sea
MeSH	N/A
NCBI Taxonomy	N/A
AGROVOC	N/A
Google Scholar	Second Thomas Shoal Ayungin Shoal BRP Sierra Madre resupply low-tide elevation South China Sea
ConceptNet	N/A
OpenCyc	N/A

Also Known As

Ayungin Shoal (Philippine name)
Buhanginan ng Ayungin (Filipino)
Rén’ài Jiāo / 仁爱礁 (Chinese)
Bãi Cỏ Mây (Vietnamese)
Second Thomas Shoal (English, after Captain Thomas Gilbert of the Charlotte)
Thomas Shoal Second (older gazetteer rendering)

Examples and Analogies

A reef that owns no sea: Under the tribunal’s classification, the shoal is like a sandbar that appears only at low tide — the land itself commands no surrounding water, so control over the area is determined by whose exclusive economic zone covers it, which the award located with the Philippines. (2016 Annex VII Award (RIAA))
An outpost made of a ship: Because the reef is mostly underwater, the Philippine presence takes the form of a rusting hull intentionally parked on it in 1999 — the BRP Sierra Madre — so that sovereignty is asserted by garrison rather than by building an island. (Wikipedia — Second Thomas Shoal)
A supply line under watch: Resupply runs to the garrison function like a repeated convoy game: small boats delivering food and rotating troops must pass opposing coast guard vessels, producing recurring standoffs that each side documents and protests. (Wikipedia — Second Thomas Shoal)
Distance as the legal yardstick: The 105-nautical-mile gap to Palawan, against the hundreds of miles to the Chinese coast, illustrates the Convention’s logic that maritime entitlements follow proximity to land, not the reach of historical maps. (2016 Annex VII Award (RIAA))

Usage Scenarios

1. Legal Reference in Maritime Disputes

The Philippine government and foreign ministries cite the shoal as the site of the award’s clearest holding — that it lies within the Philippine EEZ and continental shelf — when protesting interference with Philippine vessels and in note verbales; the case is examined in the Philippines v. China entry on this site. (2016 Annex VII Award (RIAA), Wikipedia — South China Sea Arbitration)

2. Military Rotation and Resupply Operations

The Philippine Armed Forces conduct periodic missions to deliver provisions and rotate the Marine detachment aboard the BRP Sierra Madre; the ship itself, its history, and its condition are covered in a separate entry on this site. (Wikipedia — Second Thomas Shoal)

3. Diplomatic Negotiation and Incident Management

The shoal has been the object of successive understandings between Manila and Beijing, including a reported 2017 “gentlemen’s agreement” on maintaining the status quo, which President Bongbong Marcos disavowed in 2023, and a “provisional arrangement” on resupply missions announced in July 2024. (Reuters, Rappler)

4. Journalism and Policy Analysis

Reporters and analysts treat the shoal as a barometer of South China Sea tensions, tracking resupply missions, coast guard conduct, and diplomatic exchanges as indicators of escalation or de-escalation. (Rappler, Inquirer)

Strategies

Ground Philippine operations at the shoal on the 2016 award’s findings, treating resupply as the exercise of sovereign rights in the Philippine EEZ rather than as a contestable act. (2016 Annex VII Award (RIAA))
Publicize and document incidents at sea — imagery, timelines, and protest notes — to support the legal record and to internationalize attention to conduct around the shoal. (Rappler)
Pursue practical arrangements, such as the July 2024 provisional understanding on resupply, while explicitly withholding recognition of any opposing claim, as the Department of Foreign Affairs has stated that the arrangement requires no Chinese approval for Philippine missions. (Reuters, Inquirer)
Keep the garrison’s footprint defensive and rotational, preserving the status quo while avoiding steps that would provoke escalation or be characterized as fortification. (Wikipedia — Second Thomas Shoal)
Coordinate with like-minded states in statements and joint exercises that reinforce the rule of law context in which the award sits. (Rappler)

Security and Safety Measures

Brief resupply crews on de-escalation procedures and rules for responding to blocking maneuvers, water cannons, and lasers, hazards documented in incidents since 2021. (Wikipedia — Second Thomas Shoal)
Equip supply boats and escorts with communications, recording equipment, and first-aid capability, and schedule missions around weather and sea conditions at the reef. (Wikipedia — Second Thomas Shoal)
Maintain humanitarian considerations in all intercept conduct, given that missions carry food and water to a small garrison and are often accompanied by journalists. (Reuters)
Preserve evidence and file timely diplomatic protests after each incident to keep the legal record current. (Rappler)

Historical Context

Second Thomas Shoal lies southeast of Mischief Reef, which Chinese forces occupied beginning in the mid-1990s, near the center of the Spratlys’ Dangerous Ground. In 1998, responding to Chinese construction on Mischief Reef, President Joseph Estrada decided that the Philippines would “as well put up our own structures,” and in May 1999 two Philippine vessels — the BRP Sierra Madre and the BRP Lanao del Norte — were intentionally grounded on the shoal. The Lanao del Norte was later towed away, but the Sierra Madre remained, serving as an informal navy outpost until 2014, when the Philippines declared it a permanent installation and China responded by demanding the ship’s removal. (Wikipedia — Second Thomas Shoal)

Resupply became a recurring flashpoint. Chinese coast guard vessels blocked Philippine attempts on 9 March 2014, prompting an airdrop of supplies; on 29 March 2014 a replacement-crew boat succeeded by threading shallow water where the deeper-drafted interceptors could not follow. Incidents intensified from 2021 to 2024: in November 2021 and August 2023 Chinese vessels used water cannons against supply boats; in early 2023 a Chinese ship directed a laser that Manila described as military-grade; in October 2023 ramming incidents during a replenishment run were disclosed by Philippine officials; and in June 2024 the China Coast Guard again interfered with a Philippine Navy supply mission. After China claimed in April 2024 that a “new model” had been agreed — denied by Defense Secretary Gilberto Teodoro — the two governments announced a “provisional arrangement” on resupply missions on 21 July 2024, with its details kept confidential and its interpretation disputed. (Wikipedia — Second Thomas Shoal, Reuters, Inquirer)

Challenges and Controversies

Sovereignty and Entitlement

The award’s holding that the shoal is a low-tide elevation within the Philippine EEZ and continental shelf is accepted by the Philippines and rejected by China, which did not participate in the arbitration and regards the ruling as without binding force. Taiwan and Vietnam, which also claim the Spratly group, are not parties to the award. The divergence between the legal position and the operational status quo is the defining feature of the dispute. (2016 Annex VII Award (RIAA), Wikipedia — Second Thomas Shoal)

Resupply Interference

Manila characterizes blocking of its resupply missions as unlawful interference with Philippine sovereign rights; Beijing asserts jurisdiction over the waters and describes its coast guard operations as law enforcement. Incidents involving water cannons, lasers, and collisions have drawn diplomatic protests and international attention, and each episode is narrated differently by the two governments. (Wikipedia — Second Thomas Shoal, Rappler)

The Grounded Ship

China demands the removal of the BRP Sierra Madre as a precondition it attaches to its view of the status quo, while the Philippines maintains and periodically repairs the vessel as a military outpost. The ship’s decay, and the question of whether to reinforce, replace, or withdraw it, remain matters of debate in Philippine policy circles. (Wikipedia — Second Thomas Shoal)

Secret Understandings

Disputed accounts of a 2017 “gentlemen’s agreement” and the confidential terms of the 2024 provisional arrangement have generated domestic controversy in the Philippines over transparency and over whether quiet understandings concede anything of the legal position; the DFA has insisted the arrangement entails no requirement of Chinese approval. (Rappler, Inquirer)