The water being too dark is very subjective all around. It honestly wasn’t to me, but I won’t tell someone they saw it wrong either
As for the plot adding nothing to the story, I will vehemently disagree. It very much pushes back on the whole “she gave up her voice for a man” criticism to really show how these were two people, neither of whom felt fit in in their own worlds, who found that sense of belonging in each other (and brought the two worlds together in doing so).
Lack of emotion was a problem with Triton, but not really anyone else imo.