If you are

you're a mermaid and you know it, swim like this!
(Swimming motion)
If you're a mermaid and you know it, swim like this!
(Swimming motion)
If you're a mermaid and you know it, and you really want to show it,
If you're a mermaid and you know it, swim like this!
(Swimming motion)

If you're a pirate and you know it, say “Arrr!”
("Arrr!" + fist up)
If you're a pirate and you know it, say “Arrr!”
("Arrr!" + fist up)
If you're a pirate and you know it, and you really want to show it,
If you're a pirate and you know it, say “Arrr!”
("Arrr!" + fist up)

If you're a mermaid and you know it, show your tail!
(Point to your tail / back)
If you're a pirate and you know it, find the gold!
(Pretend to dig or hold up coins)