The Mermaid emoji is a ZWJ sequence combining ? Merperson, Zero Width Joiner and ♀️ Female Sign. These display as a single emoji on supported platforms.
Mermaid was added to Emoji 5.0 in 2017.
U+1F9DC
U+200D
U+2640
U+FE0F
?♀️ Merperson
?♀️ Zero width joiner
?♀️ Female sign
?♀️ Variation selector-16