I know I shouldn't treat this seriously, but these Merman with Fish heads kind of piss me off.
It makes 0 sense from a biological view for a humanoid to have a fish head with eyes on the side, Humanoid creatures are predators. Eyes on the side of the head are a characteristic of a prey, and exist to increase their chances of staying alive, humanoids should always have both eyes looking forward. I won't even complain about how stupid it is for them to have these excessive fish parts on them. AS it's not necessary for them to really be serious to that point on a story like this. But at least do the bare minimum.