Abstract: An elongated floating boom device for containing spilled fluids such as crude oil, is disclosed. The boom device is manufactured from its constituent components at the spill site. At least one continuous sheet of a plastic material is folded along its longitudinal axis, forming two wall sections of substantially equal height. A lower weighted section is formed by introducing inexpensive ballast heavy material such as sand into the fold of the plastic sheet and creating an horizontal seal which seals the wall sections together above the ballast material along the length of the plastic sheet. A pulling means such as a chain or steel cable also is provided in the weighted section. Pillow or float sections are formed by injecting air between the wall sections above the first horizontal seal and vertically or diagonally sealing the wall sections together at intervals and then horizontally sealing the tops of the wall sections together. Alternative constructions for the bottom device also are disclosed.