Water motion is an important factor affecting the biology of marine organisms. Marine algae and plants are found throughout the world, in a wide range of hydrodynamic environments. I have used a combination of field and laboratory studies to examine how the movement of water and marine algae interact. In laboratory studies, increasing the density of the brown algae, Sargassum piluliferum, causes the water to flow around rather than through the bed. Hence, transport rates through the bed are negatively correlated with density. In the field, the continuity of seagrass (Enhalus acoroides) canopies can increase the strength of sediments within the bed, resulting in enhanced attachment strength. Finally, in coastal rocky shores, residence times of gametes within Sargassum fusiforme beds are a decreasing power-law function of wave energy, suggesting that fertilization must occur in a timescale on the order of 102 seconds.