The Waitt expedition team compares notes in the water off Explorer's stern. Photo Credit: Lance Milbrand

Fritz Hanselmann and Jim Delgado examine the hull. Photo Credit: Lance Milbrand

Jim Delgado points out features of Explorer's construction to Fritz Hanselmann. Photo Credit: Lance Milbrand

The Waitt expedition team prepares to climb inside Explorer. Photo Credit: Lance Milbrand

Fritz Hanselmann, Jim Delgado and John McKay atop Explorer. Photo Credit: Lance Milbrand

Fritz Hanselmann measures holes worn and battered through Explorer's outer hull. Photo Credit: Lance Milbrand

Archaeologist Fritz Hanselmann, INA Director Clyde Smith and naval architectural draftsman John W. McKay pose off Explorer'€™s bow. Photo Credit: Lance Milbrand

Fritz Hanselmann measures corrosion holes at Explorer'€™s stern. Photo Credit: Lance Milbrand

Fritz Hanselmann measures corrosion holes at Explorer'€™s stern. Photo Credit: Lance Milbrand

The fluctuating tides and waves help batter Explorer apart. Photo Credit: Lance Milbrand

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

With survey gear in position, the Waitt expedition team prepares to depart the dock on Protector. 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 and Fritz Hanselmann return to Protector with news of their exploration at the base of the fort. Photo Credit: Lance Milbrand

INA Chairman Donald Geddes and archaeologist Fritz Hanselmann at San Lorenzo. Photo Credit: Lance Milbrand

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

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