if we are talking about full concious mermaids like a regular human, they probably don’t like him at all, it would be easy to see why, Pitch wouldn’t even be shocked about it, hell, he wouldn’t trust himself after the current events

if we are talking about more animalistic mermaids (which those are my favorites btw becuase humanoid sea monster yes) I see them at some 50/50 relationship, some liking him, some don’t, probably many of them would like to spy his dates with Sandy, I mean, the dark abyss of the depth of sea and the shine of golden coins, what is not to love there?

if those are either the eldritch pair or the old men, probably a lot of chaos like hell yes, they sole presence would start affect the other people’s activities (food suddenly tasting like the first time you had an ice cream and cold’s medicine, the movie suddenly getting mixed with others films) the funny thing of it would be that none of them would actually be doing this that much on purpose, sort of coincidence having in mind that they just affect reality by nature

for example, the first time Shadow Pitch played to be human probably went kind of like that, Pitch was awful at trying to look human, it was terrible, that night people reported to the police about having seen some devil stalking certlain blond man, the next time they tried was on a halloween night and Pitch didn’t even bother on looking different, they went to the cinema and watched Nosferatu, Pitch liked it and laughed at many parts, Mr sandman took them to a couple little restaurants and they would go away leaving people with a tiny of dash confusion and drownsiness about if they served a certlain particular couple