Galveston Bay is one of the larger bays in the U.S. Average depths are 10 to 12 feet over a flat, smooth and muddy bottom due to centuries of shrimp trawlers dragging their kicker chains across the bottom. Overall, it is more than 30 miles from the GIWW north to Baytown and 30 miles across from Texas City to the end of East Bay. The shores are flat and marshy in some places with very few distinctive features.