![1girl bad_id bad_pixiv_id blue_eyes blue_hair drill_hair head_fins highres japanese_clothes kan_(aaaaari35) kimono mermaid monster_girl sash smile solo touhou wakasagihime wavy_hair rating:s score:5 post #2281951](/cdn_image/preview/f0/49/f0494350460a5bb86e826d14111f69b7.jpg)
For mermaids with tails that give a more fishlike impression, as opposed to designs that resemble legs wrapped in scales. Especially if the tail fins are also correct for the type of sea creature used as a basis.(Vertical for fish. Horizontal for sea mammals.)