The H2X Challenger 18D features the additional depth for greater buoyancy and an uninhibited exercise space and swim area. Make the most of your training with the H2Xercise Fitness System which comes as standard. The Challenger range bridges the gap between fitness and performance, allowing you to take your training to the next level. The VIP airless jet propulsion system with 6 strategically placed jets creates a smooth, wide current of water that can challenge a novice or elite swimmer with the press of a button.