A coating film capable of being peeled off in the shape of sheet to facilitate a coating film removal work, and is less likely to peel even after long periods of use on an underwater structure is provided. The coating film comprises an undercoat layer to be bonded to an underwater structure, and an antifouling layer bonded to the undercoat layer, wherein: a 100-gram underwater constant load peeling degree of the coating film is less than 5; a ratio of a tensile breaking strength of the coating film to an adhesive force of the coating film with respect to the underwater structure, as measured after immersing the coating film in pure water at 60 C. for 5 weeks is 1.5 or more; and a 1-mm square cross-cut stretching-caused peeling degree of the antifouling layer with respect to the undercoat layer is 0.05 or less.

A system including a subsea treatment system configured to inhibit biological growth along one or more surfaces of a subsea equipment, wherein the subsea treatment system includes a light treatment system including one or more light sources configured to output light to inhibit biological growth; or an acoustic treatment system including one or more acoustic devices configured to output acoustics to inhibit biological growth, or a combination thereof.