@interestingengineering: Dutch builder U-Boat Worx has delivered the Super Sub, a three-person submersible it says is the fastest private sub ever built, with a top underwater speed of 10 knots. Instead of being pushed along by thrusters alone, it uses rear hydrofoils to fly through the water, banking and diving at steep angles. The first unit has passed DNV certification and sea trials in Curaçao and has already been handed to its owner.