There were many different mermen who were being sold off, it wasn’t fully legal around where you were and these creatures weren’t known to exist by most

There seemed to be one that was staying to the shadows of his cramped enclosure as much as he could away from view though you noticed his eyes were glowing clearly, one red eye one white eye through the shadows staring straight at you ever since you entered the place, not blinking once or looking away, observing you specifically