The 'burst-and-coast' method of swimming involves alternating stages: the fish power forward in a 'burst' and then hold their body straight to 'coast'. Dr Müller and her colleagues might have found what it is that prevents larvae of the zebrafish from reaching top speeds: the larvae cannot maintain their body in a horizontal position while coasting. The research team think this is because larvae don't have the help of an adult swimbladder and have only small, ineffective side-fins. This lack of control in early days means that the larvae suffer a lot of drag during the coasting phase and this could be something that affects other types of fish. "Many fish larvae hatch without fully formed pectoral fins and all hatch without a swimbladder, so similar problems could occur for them", predicts Müller.