 On average , the system is 3 meters ( 9 @.@ 8 ft ) deep , and covers approximately 497 square kilometers ( 192 sq mi ) . It is the fourth largest estuarine system in Texas behind Galveston Bay , Laguna Madre and Matagorda Bay . The two main extensions are : Nueces Bay , which extends west to the mouth of the Nueces River , and Oso Bay , which extends south to the mouth of Oso Creek . Every second , approximately 34 cubic meters ( 9 @,@ 000 U.S. gal ) of water flows into the bay . The exchange with the Gulf of Mexico occurs at Aransas Pass . As a result of the seawater exchange , the bay 's salinity is 22 parts per thousand ( ppt ) , which is lower than the seawater average of 35 ppt . 
 On average , the system <a href='drop_aux' title='1'><mark>is</mark></a>3 meters ( 9 @.@ 8 ft ) deep , and <a href='uninflect' title='2'><mark>covers</mark></a> approximately 497 square kilometers ( 192 sq mi ) . It <a href='drop_aux' title='3'><mark>is</mark></a>the fourth largest estuarine system in Texas behind Galveston Bay , Laguna Madre and Matagorda Bay . The two main extensions <a href='drop_aux' title='4'><mark>are</mark></a>: Nueces Bay , which <a href='uninflect' title='5'><mark>extends</mark></a> west to the mouth of the Nueces River , and Oso Bay , which <a href='uninflect' title='6'><mark>extends</mark></a> south to the mouth of Oso Creek . Every second , approximately 34 cubic meters ( 9 @,@ 000 U.S. gal ) of water <a href='uninflect' title='7'><mark>flows</mark></a> into the bay . The exchange with the Gulf of Mexico <a href='uninflect' title='8'><mark>occurs</mark></a> at Aransas Pass . As a result of the seawater exchange , the bay <a href='null_genetive' title='9'><mark>'s</mark></a>salinity <a href='drop_aux' title='10'><mark>is</mark></a>22 parts per thousand ( ppt ) , which <a href='drop_aux' title='11'><mark>is</mark></a>lower than the seawater average of 35 ppt . 
On average , the system 3 meters ( 9 @.@ 8 ft ) deep , and cover approximately 497 square kilometers ( 192 sq mi ) . It da fourth largest estuarine system in Texas behind Galveston Bay , Laguna Madre and Matagorda Bay . Tdatwo main extensions : Nueces Bay , which extend west to the mouth of the Nueces River , and Oso Bay , which extend south to thdaouth of Oso Creek . Every second , approximately 34 cubic meters ( 9 @,@ 000 U.S. gal ) of water flow into the bay . The exchange wit the Gulf of Mexico occur at Aransas Pass . As a result of the seawater exchange , the bay  salinity 22 parts per thousand ( ppt ) , which lower den the seawater average of 35 ppt .