Abstract: A watertight ready-made or foldable storage bag suitable for preserving and protecting items against flood hazards, preferably has a lower part in the shape of cuboid made of watertight material, and an upper part with an upper edge watertightly sealed. The bag is foldable from a planar form into a suitable shape immediately before use which saves space for large items. For smaller items the bag may be pre-folded, so that the preserved item can be placed therein, and closing the bag watertightly with its upper part. The dimensions of the bag vary depending on those of the item placed within. In an alternative option the lower and upper parts of the bag are separate parts. The lower part ensures complete watertightness of the item from the sides and below, and upon flooding, floatability of the item, while the upper tent part ensures watertightness of the item against precipitation from above.