6:16 window. The “window” was probably an opening for light and ventilation extending circumferentially around the ark, with a parapet to keep out the rain. The one large door in the side was to be closed only once (after the animals were in) and opened only once (to release them a year later).
6:16 third stories. The three decks may have been laid out as follows: large animals on the bottom; small animals and food storage on the middle deck; family quarters, possessions, records, etc., on the top deck. Water could have been stored in cisterns on the roof and piped throughout the ark where needed. Overhead water storage could also have provided fluid pressure for various other uses.