Which feature is generally characterized by grass, rushes, and shallow waters?

Marshes are ecosystems that are prominently characterized by the presence of herbaceous plants such as grasses and rushes, alongside shallow waters. These environments typically have saturated soils, and they can be found in areas that experience periodic flooding or are seasonally wet. The combination of shallow water and soft-stemmed vegetation distinguishes marshes from other wetland types.

Swamps, while also wetlands, are primarily dominated by woody plants like trees and shrubs, which do not align with the description provided in the question. Deltas are landforms created by sediment deposition at river mouths where they meet a body of water, creating a mixture of ecosystems including marshes, but they do not specifically refer to areas characterized by grasses and rushes alone. Taiga, on the other hand, is a biome defined by its coniferous forests and cold climates, completely differing from the wetland characteristics described. Therefore, marshes are the best match for the environment described.