In another thread about output devices, someone linked to a package marketed by Ryonet. When describing their waterproof film, they included something I don't think is accurate. "Using an Epson printer for film output requires waterproof films."
It was always my understanding that the emulsions on film were designed for the two inks. Dye, or pigment. For many years, folks with Epson 3000 printers using dye based inks did fine with the clearer non-waterproof inks. As more folks started using printers for double duty, including transfers, pigment based inks seemed to become more common, and more and more of the slightly frosty waterproof films, and their pigment- receptive emulsion became the easiest to find.
Perhaps someone with a little more technical expertise than I have could verify or clarify this.