Second Thomas Shoal is a submerged reef located in the Spratly Islands. The Philippines first took possession of the feature in 1999. The Philippine outpost on Second Thomas Shoal is the BRP Sierra Madre, a Philippine Navy transport ship intentionally grounded on the reef and maintained by a contingent of marines. The Sierra Madre can be seen below in the detail gallery.
U.S. Board of Geographic Names: Second Thomas Shoal