One of many iron cannon on the grounds of the Castillo. Photo Credit: Lance Milbrand

The surf breaks over the fangs of Lajas Reef. Photo Credit: Lance Milbrand

An unexploded mortar shell from the 18th century lies in the shallows below San Lorenzo. Photo Credit: Lance Milbrand

Notes from each assessment dive were made on frosted mylar. Photo Credit: Lance Milbrand

An encrusted bottle seen at the edge of the reef. In order to preserve such objects for more detailed study, all artifacts were left in place and not disturbed. Photo Credit: Lance Milbrand

This brick, with a piece of exploded mortar shell on it, may date from the 1740 attack and destruction of San Lorenzo. Photo Credit: Lance Milbrand

This pillbox guarded the entrance to the Chagres after 1911 and through WWII. Photo Credit: Lance Milbrand

The Rio Chagres. Photo Credit: Lance Milbrand

This bottle was observed on Lajas reef, where many ships are said to have met their fate. Photo Credit: Lance Milbrand

Holes and gouge marks show where treasure hunters have worked on Lajas Reef and removed artifacts. Photo Credit: Lance Milbrand

This enclosure protected a sentry on guard at Fort San Lorenzo. Photo Credit: Lance Milbrand

Iron cannon at San Lorenzo. Photo Credit: Lance Milbrand

The ruins of the fortified barracks at San Lorenzo. Photo Credit: Lance Milbrand

Waitt Institute Dive Safety Officer, Joe Lepore, and Sonar Analyst Steve Bilicki take a look at Lajas Reef. Photo Credit: Lance Milbrand

Waitt Institute Dive Safety Officer, Joe Lepore, and Sonar Analyst Steve Bilicki assess the wind and sea conditions. Photo Credit: Lance Milbrand

Fort San Lorenzo and Yankee Chagres, circa 1848. Image Courtesy of Jim Delgado.

This 1850 map shows the Isthmus of Panama and the Castillo de San Lorenzo at the upper right corner. Image Courtesy of Jim Delgado.

Videographer Lance Milbrand captured footage of the Waitt Institute expedition team at work in the field. Photo Credit: Jim Delgado

Protector surveys in the middle of the mouth of the Rio Chagres. Photo Credit: Lance Milbrand

The Waitt expedition team departs for another day of surveys along the Rio Chagres. Photo Credit: Lance Milbrand

Protector running sonar and magnometer survey lanes along the Rio Chagres. Photo Credit: Lance Milbrand

Archaeologist Fritz Hanselmann. Photo Credit: Lance Milbrand

Dr. Dominique Rissolo tells the Waitt expedition team about their findings. Photo Credit: Lance Milbrand

The Waitt expedition team conducts a snorkel survey at the base of the Fort San Lorenzo. Photo Credit: Lance Milbrand

Dr. Dominique Rissolo and Fritz Hanselmann return to Protector with news of their exploration at the base of the fort. Photo Credit: Lance Milbrand

View of Lajas Reef from the parapet of San Lorenzo. Photo Credit: Jim Delgado

The entrance bridge and sallyport, from the dry moat of San Lorenzo. Photo Credit: Jim Delgado

The mouth of the Rio Chagres from the Castillo de San Lorenzo. The entire area serves as a maritime cultural landscape. Photo Credit: Jim Delgado

INA Chairman of the Board Donald Geddes first studied the submerged history of the Chagres in the 1950s. Photo Credit: Jim Delgado

The ruins of the fortified barracks still stand inside the fort, high above the Rio Chagres. Photo Credit: Jim Delgado

Principal Investigators Jim Delgado and Fritz Hanselmann at Fort San Lorenzo. Photo Credit: Lance Milbrand

Archaeologist Fritz Hanselmann and videographer Lance Milbrand prepare to dive off the mouth of the Chagres. Photo Credit: Jim Delgado

The eroding cliffs below the Castillo occasionally send portions of the fort into the sea. In 1671 and 1740, invaders also sent walls and guns crashing below. Photo Credit: Jim Delgado

Fritz Hanselmann and Lance Milbrand surface after a dive off the mouth of the Chagres. Photo Credit: Jim Delgado

Cannon ball in the shallows below San Lorenzo. Photo Credit: Lance Milbrand

This earthenware fragment dates to the Gold Rush period (1848-1860). Photo Credit: Lance Milbrand

The metal detector survey located the site of a World War II gun emplacement buried in the sand and grass. Photo Credit: Jim Delgado

The Waitt Institute team surveys with a metal detector on the beach at the site of Yankee Chagres. Photo Credit: Lance Milbrand

The Waitt expedition team pauses in an area where an anti-aircraft gun emplacement stood during World War II. Photo Credit: Lance Milbrand

Archaeologist Jim Delgado organizes land survey with the Waitt expedition team. Photo Credit: Lance Milbrand

The Waitt expedition team examines a dugout canoe left on the banks of the river. Photo Credit: Lance Milbrand

This broken plate with its deer motif probably dates to the Gold Rush period. Photo Credit: Lance Milbrand

The Castillo’s promontory looms on the opposite shore from the site of Yankee Chagres, as the Waitt expedition team meets below. Photo Credit: Lance Milbrand

The concrete dock at the mouth of the Rio Chagres was built by the U.S. military atop the site of an earlier dock. Photo Credit: Jim Delgado

This small cove is the location of the lower edges of the former town of Chagres. Photo Credit: Jim Delgado

Looking outward from inside the mouth of the Rio Chagres. The open Caribbean lies beyond. Photo Credit: Jim Delgado

The Castillo, as seen from the site of old Chagres. Photo Credit: Jim Delgado

A line in the water marks the site of a stone wharf from old Chagres. Photo Credit: Jim Delgado

Jim Delgado takes a GPS reading for a concrete mooring block for a WWII pontoon bridge. Photo Credit: Lance Milbrand

Hole left on Lajas Reef by treasure hunters searching for artifacts to take off the reef and sell. Photo Credit: Lance Milbrand

Hole left on Lajas Reef by treasure hunters searching for artifacts to take off the reef and sell. Photo Credit: Lance Milbrand

Dr. Dominique Rissolo and Fritz Hanselmann surface during the snorkel reconnaissance. Photo Credit: Lance Milbrand