How do you model a surface that "folds back" on itself? Like the hull of this ship for example: http://wordlesstech.com/wp-content/uploads/2012/01/Improving-fuel-efficiency-by-blowing-air-bubbles-on-ship-hulls-3.jpg

I feel like you should be able to with lofts maybe, but I've tried just about everything I can think of and still can't get it. All the tutorials I've managed to find seem to be for simpler curves, e.g. a vase. Help, I've been banging my head against this problem all day!