It isn't easy to ditch a plane, especially a high winged one. That is especially true in high winds which cause big waves. Normally, you always want to land into the wind so the ground speed will be as low as possible. However, when ditching in such conditions, you want to come in parallel to the waves. This means your touchdown speed is higher and there's a big risk of dragging a wingtip, causing the plane to cartwheel. The pilots did a great job of putting the plane into the water without causing major structural damage. The crew did a not so good job of fuel management, but their ditching ability is beyond doubt.

A C-130 has a fuel capacity of over 9500 gallons, with the fuel tanks in the wings. If the wings aren't damaged as appears to be the case in the photo, then you have a lot of bouyancy. It's also a pressurized plane, so if there's no structural damage to the fuselage, then the water infiltration would probably be pretty slow. They probably got out of the plane through an overhead panel in the cockpit.