Complex sentence: On 17 February 1864, "Hunley" attacked and sank the in Charleston harbor becoming the first submarine to sink an enemy ship, but soon after, "Hunley" also sank, drowning all eight crewmen.
Split into simpler sentences: On 17 February 1864, she attacked and sank the in Charleston harbor, becoming the first submarine to sink an enemy ship. Soon after, however, "Hunley" also sank, drowning all eight crewmen.