Both canyons and sandbars are fundamentally shaped by water erosion, though operating at vastly different scales and environments.
Formed by river erosion over geological timescales. Flowing water cuts downward through rock layers, creating deep, steep-walled valleys. The Grand Canyon exemplifies this—6 million years of Colorado River incision through sedimentary strata.
Formed by wave and current erosion/deposition in coastal and riverine environments. Waves move sediment alongshore, while currents create offshore deposits. River sandbars form where flow velocity drops, depositing sediment in channels.
Both are erosional/depositional landforms created by moving water—rivers for canyons (primarily erosion), waves/currents for sandbars (erosion and deposition). Both demonstrate water's power to reshape Earth's surface.