SITKA, Alaska (AP) — A fishing charter boat found partially submerged off an island in southeast Alaska last May likely capsized after its well deck flooded in rough seas, according to the U.S. Coast Guard, which investigated the incident that left five people dead, including two vacationing sisters and their partners.

More than 100 people attended the Coast Guard’s town hall-style presentation in Sitka last week on the findings of its investigation, the Daily Sitka Sentinel reported.

Investigators said survival options were limited once the 30-foot (9-meter) boat, Awakin, capsized on May 28, 2023; the vessel was not required to carry an emergency raft. The boat, which was found off Low Island, about 10 miles (16 kilometers) west of Sitka, had minimal provisions for draining water from the well deck, the Coast Guard’s lead investigator, Cmdr. Nate Menefee, said.

“The initiating event of the Awakin’s casualty was a sudden flooding of Awakin’s well deck by a large swell,” Menefee said. “This was impacted by positioning the vessel close to Low Island in shallow water and at low tide, which brought the vessel to a hazardous area, increasing the likelihood of encountering large swells and breaking surf. The navigation of Awakin near Low Island is a major factor of this incident. Flooding the vessel’s well deck and limited drainage openings would have substantially impacted vessel stability.”

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Menefee said there is a degree of uncertainty around the final minutes of the trip and added that the Coast Guard “cannot definitively say exactly what caused Awakin to capsize.” There were no witnesses and no distress calls received, the Coast Guard said.

At 2:43 p.m. on May 28, the boat’s tracking system recorded its last known location, just south of Low Island near a well-known fishing spot. One of the passengers trapped in the cabin tried five times to make emergency calls on their cellphone between 3:01 and 3:12 p.m., but no calls connected. A text message recovered from the phone’s draft messages folder read “Call 911” but was unsent.

The last photos recovered from a phone were taken at 2:43 p.m. and show a passenger holding a rockfish.

The lodge where the charter originated reported the boat overdue around 5:30 p.m. A Coast Guard helicopter launched at 6:55 p.m. and shortly thereafter located the boat, partially submerged. While the Coast Guard aims to maintain 30-minute readiness for launching a helicopter, it took longer that day because of fueling issues.

Those who died were charter guide Morgan Robidou, 32; Brandi Tyau, 56, and her partner Robert Solis, 61, of Canoga Park, California; and Danielle Agcaoili, 53, and her husband, Maury Agcaolli, 57, of Waipahu, Hawaii. Autopsies determined drowning was the cause of death of the four whose bodies were recovered.