You've seen the memes of scammers straight up asking for credit care info? This is sort of a play on "dumb scammer barely qualified for the job" type of meme. A good siren would probably text some actually enticing stuff - like that the water is very pleasant and that she's skinny dipping. This one is probably frustrated that she can't allure anyone, so she's desperately trying anything and everything.

If a siren could text this is what they'd text.

That's kind of the whole of the joke. It's funny because they're not real and can't text.