I think they always have a pot of water going. You'd really kinda have to to get things rolling (boil, get it? HAHA)
Ingredient wise: From what I read somewhere or another the 2 competing chefs have an idea -- the category -- of the ingredients, they just don't have a specific. Each side (I say side because of the Otta faction) gets to pick 5 categories of foods they would like to compete with and that somehow gets whittled down a bit. A subcategory is announced. The actual ingredient from that category is a surprise at time of competition. (Kind of makes you wonder how yogurt ever got to be an ingredient, huh!) This is also how the chefs know to bring particular props or surprise ingredients beyond what would be found in the pantry.
BTW, I couldn't quite get excited over the turkey sashimi in the Christmas special they re-ran the other night - how 'bout you?