Abstract: An underwater window for vessels which is provided to cover an opening made on the hull has a first transparent plate curved to form a convex surface bulging toward the outside of hull outwardly from the hull. One or two additional transparent plates are provided to cover the concave space which is formed on the cabin side by the first curved plate. The space formed by the curved plate and the additional plate, or plates, is filled with a liquid. The liquid contains distilled water and an algaecide, such as CuSO.sub.4 and has its pH adjusted to with the range of 7.0-7.6.

Abstract: A formed product of a high molecular compound having a glass transition temperature of not more than about 60.degree. C., which is substantially free of halogenated solvents harmful to the human body, is produced by mixing the high molecular compound, a halogenated solvent and an organic solvent other than the halogenated solvent which is compatible with the solvent and is less apt to dissolve the high molecular compound to prepare a solution and then maintaining the solution at a temperature around the boiling point of the halogenated solvent.