Seafloor of the Galveston is full of sand and sediment which is suspended in and around the bay.
Step-by-step explanation:
The water in and around the Galveston bay. The reason for the water to be brown in that area is because of the sediments and other material which are suspended to be brown in the water.
The water in the Galveston is shallow as a reason of which the sediments and the sand turn over in that area is high, making it look brown in color instead of blue. Thus water seems to be dirty and muddy at many point of time.