She starts fingering his gills and he repeatedly asks her to stop after which she basically molests him against his wishes.
It’s horrible to watch as a viewer and Chase Crawford recently said he agreed watching the scene was actually worse than having to film it with the actress.
The moment in question – and we’re about to get into some Season 1 spoilers here – is a scene in which The Deep starts hooking up with a girl who clearly wanted to mess around with someone with an unusual body type.