In modern nuclear submarines that can remain underwater for many months at a time, the only limit to the length of time the submarine can spend underwater is the amount of food which can be carried to sustain the crew and a patrol duration which does not compromise crew fitness and alertness. The food is of excellent quality like you would expect in a quality hotel. It must be kept and prepared in spotless conditions to make sure the crew do not fall ill at sea. The submarine has deep freezers and refrigerators and dry provisions stores and will typically prepare up to around 320 meals a day on average.
