is particularly true for the larval fishes with higher metabolic rate and smaller size which makes them more susceptible to predators. The swimming ability of a reef fish larva helps it to settle at a suitable reef and for locating its home as it is often isolated from its home reef in search of food. Hence the swimming speed of reef fish larvae are quite high (≈12 cm/s - 100 cm/s) compared to other larvae. The swimming speeds of larvae from the same families at the two locations are relatively similar. However, the variation among individuals is quite large. At the species level, length is significantly related to swimming ability. However, at the family level, only 16% of variation in swimming ability can be explained by length. There is also a negative correlation between the fineness ratio and the swimming ability of reef fish larvae. This suggests a minimization of overall drag and maximization of volume. Reef fish larvae differ significantly in their critical swimming speed abilities among taxa which leads to high variability in sustainable swimming speed. This again leads to sustainable variability in their ability to alter dispersal patterns, overall dispersal distances and control their temporal and spatial patterns of settlement. Hydrodynamics Small undulatory swimmers experience both inertial and viscous forces, the relative importance of which is indicated by Reynolds number (Re). Reynolds number is proportional to body size and swimming speed. The swimming performance of a larva increases between 2–5 days post fertilization (d.p.f.). Compared with adults, the larval fish experience relatively high viscous force. To enhance thrust to an equal level with the adults, it increases its tail beat frequency and thus amplitude. Tail beat frequency increases over larval age to 95 Hz in 3 days post fertilization (d.p.f.) from 80 Hz in 2 days post fertilization (d.p.f.). This higher frequency leads to higher swimming speed, thus reducing predation and increasing prey catching ability when they start feeding at around 5 days post fertilization (d.p.f.). The vortex shedding mechanics changes with the flow regime in an inverse non-linear way. Strouhal number (St) is considered as a design parameter for vortex shedding mechanism and can be defined as a ratio of product of tail beat frequency with amplitude with the mean swimming speed. Reynolds number (Re) is the main deciding criteria of a flow regime. It has been observed over different type of larval experiments that, slow