The Merman emoji is a ZWJ sequence combining ? Merperson, Zero Width Joiner and ♂️ Male Sign. These display as a single emoji on supported platforms.
Merman was added to Emoji 5.0 in 2017.
U+1F9DC
U+200D
U+2642
U+FE0F
?♂️ Merperson
?♂️ Zero width joiner
?♂️ Male sign
?♂️ Variation selector-16