I mean, the point of a mermaid isn’t that it’s a sexy looking fish, it’s that other than its tail, it looks like beautiful human women. In some stories, sailors don’t even realize they’re taking to mermaids because their tails are underwater. Also, mermaids were generally considered bad omens or malicious entities, and when they did seduce humans, it was usually to kill them, so it’s not like the folklore was very pro-mermaid sex.
Sooner or later, you will get trapped somewhere forever. Over the course of an infinite lifespan, the odds that a building collapses on you or a tunnel caves in on you basically become 100%. Someday, you will fall into the hole that you will stay in until the sun explodes, and then you will drift in the void until the heat death of the universe.