Propelled by a shimmering silicone tail, Katrin Gray spins underwater, blowing kisses to the audience as her long, copper hair floats around her face. Her seemingly effortless movement is anything but – a professional mermaid’s free diving and performance skills require training, practice and total concentration.

Mermaiding has become a global cottage industry, with pageants, conventions, retreats and meet-ups, where people gather in “pods” to practise their dolphin kicks. Makers create bespoke tail flukes, bejewelled bras, mermaid hair and even prosthetic gills for professional and hobbyist “seasters”. There is even a Netflix reality series called MerPeople, which documents the occasionally perilous journey of several aspiring professional merfolk. “No dead mermaids” is the motto of one business featured.

Gray, who goes by Mermaid Kat, is an industry veteran. While working as a scuba diving instructor in Phuket, a childhood obsession with Disney’s Little Mermaid led to her asking a wetsuit maker to fashion a cover for her monofin.

“Phuket is quite a small island and it didn’t take too long for people to notice a crazy girl swimming around in a mermaid tail,” she says. People asked her to perform at birthday parties and public events, and soon after she was working as a mermaid full-time. “It just took off.”

In 2012, Gray founded the world’s first mermaid school. Since then, more than 12,000 students have attended her classes and workshops in Germany, Thailand and Australia.

On top of learning to dive underwater with your legs tied together – using an undulating motion similar to a butterfly kick – Gray’s beginner lessons cover safety, surface swimming and the importance of being an “ocean ambassador”. Her multi-day international retreats, meant for aspiring full-time performers, sell out months in advance.

Melbourne-based Tara Schwarz, known as Mermaid Tarielle, has also “made a career out of swimming in glittering tails”. Last year, she attended a mermaid convention in Germany, where she held workshops on underwater makeup.

“It is a skill in itself to get a full makeup look that not only stays on in the water, but also pops,” she says.

There are occupational hazards behind the magic. Keeping your eyes open underwater means blurry vision; sinus and ear infections are common; hypothermia and sea sickness are a possibility, and, when you’re finished, getting out of skin-tight silicone is a struggle.

Gray and Schwarz have had their share of extreme aquatic adventures. Gray has starred alongside an inquisitive hammerhead in an anti-shark-finning campaign video in the Bahamas and remembers feeling distinctly overwhelmed as a 4-metre long American crocodile swam overhead in Mexico.

“To do this kind of work you need to be training regularly, to work on your lung capacity,” Schwarz says. A calm state of mind and low heart rate determine “how much power you have to put into the movement and how long you can stay underwater”.

Mermaid performances are a chance to share ocean conservation messages. At birthday parties Schwarz, who has a background as a children’s entertainer, will play a game similar to pass the parcel, “in which I tell them about how I collected all this treasure from the ocean but I also found all this rubbish,” she says.

“We agree it’s such a shame that I had to spend all the time cleaning up the rubbish before I was able to collect the treasure.”

Ocean conservation is also the main game for Perth based Mongplearn Uttama, AKA Mermeow Awn. “I started off doing corporate events … but really prefer just being involved in events that help community,” she says. “I love doing beach and underwater cleanups as a volunteer mermaid.

“We use the power of the mermaid lure to get people to come and help us pick up rubbish. It seems to work. When they know that mermaids will be there, they come.”

Mermaiding has been a lifeline for Uttama. “I lost someone very important to me and I was dealing with depression,” she says. But when she first dived into a pool, she felt free.

“I didn’t cry in the water. It is so quiet and it mutes your senses. I didn’t think of anything … I just swam the tears away. Once I put the mermaid tail on, my life was changed for ever.”

Stories like Uttama’s are common among merfolk. “People who want to be mermaids and mermen are people who want to invite more colour and fantasy into their lives, and there is often a reason for that,” Gray says.

Like any community, it has its share of drama and gossip behind the scenes, which is why, as a mermaid mentor, she emphasises the important of finding the right pod. And when it comes to more spectacular stunts, both Gray and Schwarz say a skilled safety team is essential too.

“If anything goes wrong, they are able to come in with air no matter where I am or what’s going on,” Schwarz says. “When I do a deeper dive, I always have people … who understand the technical side of free diving, to be able to offer the right kind of support.”

“If it was always easy, I wouldn’t find it fun any more,” Schwarz says. “There is a part of me – the free diver – that loves to push myself. The beauty of mermaiding is you get to do that while looking beautiful and graceful.”