Even though the Bay Area is surrounded by water, a lot of people don't know much about the nautical vessels that roam our waters, and many of you have asked Bay Curious about them.

So we turned to the experts — the Coast Guard's Vessel Traffic Services (VTS) — to help us find the answers to your many questions.

What's the difference between the various vessels on the bay?

Most of the large boats on the bay are either barges or cargo ships.

A barge is a floating platform. It doesn't have a motor, like the trailer part of a tractor-trailer.



Bay Curious is a podcast that answers your questions about the Bay Area. Subscribe on Apple Podcasts, NPR One or your favorite podcast platform.



There are many kinds of barges. 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.

Many of these dredging barges are anchored at the Treasure Island East Moorings, east of Treasure Island and north of the Bay Bridge. Empty barges are tied there to floating mooring balls, which are anchored to the bay floor.

When silt and rocks are dredged from the bay floor, they're piled onto a barge. Once that barge is full, it's towed away to be dumped, and then one of the empty barges parked at the mooring group is brought in.

"It’s like a big parking lot is what it is," said Michael Roja, who leads VTS for the Coast Guard. "This is the biggest mooring group in the bay."

