Numerous side branches join the Severn mainstem as subestuaries throughout its length. Usually called "creeks" they are typically irregular in shape, with some having broad mouths and water depths up to 15-20 feet. These creeks make excellent anchorages for recreational boaters. The creeks along the south shore are longer due to the greater breadth of the watershed there. Sandbars have narrowed the mouths of some creeks. These bars are built up by wave action or eroded material from nearby cliffs. When the sandbars are large, only small entrances remain, and the enclosed waters are often termed ponds or, if longer, lakes.
Although subject to tidal influence, ponds and the heads of creeks support freshwater plant and animal life if they are fed by significant streams. Bottom sediments in the tidal tributaries consist of fine silt, although the shallows are somewhat sandy.