The mobile aquatic centre adopted by France's northeastern Moselle region is bringing crucial swimming classes to towns and villages that lack pool facilities.

"I think this tool is fantastic for the children, because they can do aquatic activities at home, without too much travel," said Beatrice Simon, a school principal in Verny, a town of 2,000 people.

A group of first-graders made the two-minute walk from their classrooms to the pool truck for their lesson. Normally they would have to drive for 30 minutes to the next town.

Inside the blue trailer, students in groups of five use the pool that is eight metres long, two metres wide and 30 centimetres deep. There are also showers and changing facilities.

The truck is hooked up to the local water and electricity supply.

Lifeguard Marc Levy told AFP the mobile pool was "surprising", operating like any other with a heat pump, drainage and filtration system.

The truck arrived in Verny in January, offering a daily session over eight to 10 days for first- and second-graders, enough for some to earn a swimming certificate, before moving on to another town.

The consistency beats the one-off trips to far away facilities that are often overcrowded, teacher Thomas Rochet said while supervising lessons.

This small-group instruction is "almost personalized" and more "efficient" than typical classes, added Clarisse Naud, a physical education adviser.

The pool truck required about 775,000 euros (just over $922,642) in regional funding.

The lessons are focused on safety in a region where officials say up to 40 percent of adolescents cannot swim, while across France, drownings remain the leading cause of accidental death among under-25s, according to public health figures.