I was reading this article about someone attempting to stay underwater for 5 days, which got me wondering how you eat underwater!
I suppose you can survive on smoothies and other 'suckable' food-stuffs. You know, things that will go through a straw. But would it be possible to eat real food?
Then as I read further through the article, it sounds like the lake he's in isn't the type of fluid you'd want your food stuffs to come in contact with! Maybe sticking to a liquid lunch is the right way to go.
Then there is the issue of "waste disposal". Does he plan to wear a diaper for five days? Surely he would need to change it once a day to avoid nappy-rash, which presents a floater risk. I'm not sure he's sufficiently thought this thing through.
I applaud his efforts to promote environmental stewardship though. Good luck Allen!