The extraction of marine energy, through either tidal or wave array operation, will clearly influence the hydrodynamics of a region. Although the influence on tidal currents and wave properties is likely to be very small for most extraction scenarios, the influence on bed shear stress is likely to be greater, because bed shear stress is quadratically related to tidal currents and wave orbital velocities. Further, the transport of sediments is a function of tidal current and wave orbital velocity cubed. Therefore, even small modifications to the flow field through tidal or wave array operation could lead to significant impacts on regional sediment dynamics. In this paper, we explore the impact of tidal energy devices/arrays on regional sediment dynamics. We also discuss the sedimentary processes associated with tidal lagoons, such as scour and sediment drift outside a lagoon, and sediment accretion inside a lagoon.