San Francisco Bay Is Filled with Boats, but What Do They Do?

Spud barges, for example, use a big steel shaft or spud that goes down to the bay floor to stay anchored in place. Other barges are used for dredging and construction, which is constantly happening to keep certain channels in the bay deep enough for big vessels to get in and out of the ports. Empty barges are tied there to floating mooring balls, which are anchored to the bay floor.

Source: www.kqed.org