But they have to surface because the V-Million wasn’t made to run at twenty-nine knots forever; she burns fuel, and hydrogen peroxide, at a ridiculous rate when both of her six-thousand-horsepower turbines are spinning. There is plenty of fuel remaining. But she runs out of hydrogen peroxide at about midnight. She has a few miserable batteries, and electric motors, that just barely suffice to get her up to the surface. But then she has to breathe air for a while, and run her diesels.