I asked this keeping Food Fresh question before, but I don't think I explained myself very well. I would like to know if, in the case that?
The foods you've described don't keep well in air tight.containers either... submerged or not. I live in a hot humid climate and keep tomatoes in a bowl, potatoes in the cupboard and bread in the freezer. Standing water will happily come up to room temp. Here that can be 35-40oC. Sealed containers would become petrie dishes very quickly. Every time you open, close and resubmerge them you'll be cross contaminating and will have to change the water. Standing water also attracts every insect around. You can't keep it clean, even indoors. Some cultures did, however, store food in streams or creeks with running water in netted bags. This worked because the running water is generally colder and cleaner than standing water. Maybe not so much these days though..
The water would warm up over time.