As for why the umbrella term for the hobby is MERMAIDing, I think it has a lot to do with popular terminology and the way it sounds.
The Mermaiding hobby involves freediving, swimming, underwater activities, and group gatherings. The big difference is that people involved in that activity use mertails to swim.
It's actually a great physical activity that keeps people in very good shape. It also gets people involved in doing things in nature, like the ocean and freshwater springs.
Despite potential perceptions, it's actually an extremely healthy activity for social interaction, mental health, and physical health.
