Undulation or undulation technique refers to a wave-like deflection of the body when swimming . A slang term for it is dolphin wave .
In the dolphin swimming style , the undulation is the main component of the movement in addition to the arm and leg movement; But this technique is also gaining ground in breaststroke swimming , especially in the top area. What is striking is the up and down of the upper body when swimming, which resembles a snake twisting horizontally to the surface of the water . With dolphin, crawl and backstroke swimming , it is allowed during the competition to dive up to 15 m under water with the help of the dolphin wave after every turn and after the start. This way, advanced skiers are faster than if they would swim the conventional way. In breaststroke swimming, it has been allowed since January 1, 2006 to perform exactly one dolphin kick after the start and each turn.