Researchers at Duke University might have solved one of the enduring mysteries of the Civil War: they think the Confederate submarine H.L. Hunley — the first sub ever to sink an enemy ship — sank immediately from the force of its own torpedo, per Popular Science.

• What happened: The shock wave from the sub's torpedo struck the craft so hard that it damaged the soft tissues of the crew's lungs and brains, perhaps killing the entire crew of eight immediately.
• How they found out: The research team built a scale model of the Hunley and blew it up in a pond in an attempt to replicate the effects of the shockwave.
• Fool me twice: Before its final, fateful journey, the Hunley had already been sunk and raised twice — killing 13 previous crew members in the process.