 A deepwater channel connects Galveston 's harbor with the Gulf and the Gulf Intracoastal Waterway . According to the United States Census Bureau , the city has a total area of 208 @.@ 4 square miles ( 540 km2 ) , of which 46 @.@ 2 square miles ( 120 km2 ) is land and 162 @.@ 2 square miles ( 420 km2 ) and 77 @.@ 85 % is water . The island is 50 miles ( 80 km ) southeast of Houston . 
