They pick up some speed but for most ships I guess their terminal velocity will be lower than 100 mph. People have suggested Titanic hit the bottom at around 30 mph. Individual pieces would probably hit faster if nicely streamlined.17,000 feet of water, that's more than 3 miles. I've always wondered how fast these huge steel ships are going when they finally hit bottom. Do they just sort of float down and settle on the bottom, or are they runaway freight trains slamming into the bottom at 100 mph?