With huge chains and honking cranes, that's how. Example: This Republic of Korea Navy's corvette - half of it, actually - floating over the sea's surface. And before you cry "PHOTOSHOP!", check out the scene from a distance.
It's the Cheonan, a South Korean Pohang-class corvette that broke in two on March 26. According to the investigation, it was a torpedo fired from a North Korean Yeono class miniature submarine. A few weeks later, on April 15, the South Korean Navy recovered the stern part from the bottom of the sea using this giant floating crane.