Endless swimming pool illustration

Quick answer：

An endless swimming pool, also known as a perpetual pool, is a type of swimming pool designed to simulate the experience of swimming in the ocean. It features a conveyor belt system at the bottom of the pool, which moves water continuously in one direction. This creates a current that allows swimmers to move forward without swimming against the resistance of still water. The illustration would typically show a long, narrow pool with the conveyor belt system visible, along with swimmers using the current to propel themselves through the water.