5 harrowing details about the death of school administrator Shelley Tyre on Dateline, explored

The mysterious death of Shelley Tyre is the subject of the Dateline: Unforgettable episode The Last Dive. Shelley was a school principal working in Boston who resided in Rhode Island with her husband, David Swain.

The husband and wife duo loved diving and went for a scuba trip to Cooper Island in March 1999. However, when it was time for the couple to return to the shore, only David returned and Shelley was found dead in the ocean. Though the death seemed accidental at first, her husband later became the prime suspect in her murder case.

Dateline: Unforgettable explored how the case got complicated over time, with some believing Shelley died due to faulty scuba diving gear, while others thought David killed her. Here are 5 horrific details surrounding Shelley Tyre’s drowning and death, as seen in the Oxygen true-crime series.

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5 details about Shelley Tyre’s death explored in Dateline: Unforgettable

1) Shelley Tyre’s diving gear was damaged

Shelley was found dead at the bottom of the ocean during a diving trip on March 12, 1999, where she went with David. At the time, her diving gear was found to be in terrible condition. Her scuba mask was broken, the mouthpiece from her snorkel was missing, and the pin holding her mask strap was gone.

One of her swim fins was also stuck upright in the sand without its strap. Though Shelley’s autopsy called her death an accident, the condition of her gear made everyone wonder if it was a homicide case, and the suspicion ultimately fell on David.

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2) David’s timeline of events did not match up with the evidence

As Dateline: Unforgettable showcased, David said he and Shelley had split up underwater during their dive. While Shelley went to count fish, he was taking pictures of marine life.

But prosecutors argued that Shelley’s air tank showed she ran out of air just eight minutes into the dive. This happened when David admitted he was still near her. Hence, the investigators questioned how he did not notice his wife getting drowned.

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3) David was writing letters to another woman before Shelley’s death

David owned a dive shop, which was not doing well around the time of Shelley’s demise. He was relying on her for income. The couple had a prenup that said neither would get money if they divorced, but Shelley had left David $600,000 in her will.

Meanwhile, David had been writing letters to another woman, months before the incident, and even called her his ‘soulmate.’ Prosecutors believed that David wanted to be free of his marriage but did not want to face financial trouble, and hence, he might have decided to kill his wife.

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4) Witness recalled Shelley’s final moments

Shelley’s body was found by a fellow diver, Christian Thwaites. He saw her in a horrifying state as she lay face up on the ocean floor with her eyes open. David was trained in CPR and tried to revive her briefly.

Dateline: Unforgettable showed how Christian testified in the case and said David told him not to continue rescue efforts and not to send a ‘Mayday’ distress call. This raised even more questions about his possible involvement in the accident.

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5) The incident led to a legal fallout

As seen on Dateline: Unforgettable, Shelley’s parents filed a lawsuit against David, saying he was responsible for her drowning. In 2006, a jury agreed and ordered him to pay $3.5 million in damages. This pushed authorities in the British Virgin Islands to reopen the case.

In 2009, David was found guilty of murder and sentenced to 25 years in prison. However, his conviction was overturned two years later, citing the jury instructions were unfair and that too much time had passed since the incident.

Even though he was released, Shelley’s family never stopped believing he was guilty. David later died in 2022 at his home in Rhode Island.

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