The bay has a surface area of 4,173 acres (1,689 ha) and features high water quality, vast oyster reefs, and surrounding salt marsh habitat.

[4] Low global sea levels permitted the landmass of what is now Texas to stretch much farther south than it does now, and the Trinity River excavated a 170-foot-deep (52 m) canyon on its way to the ocean through what is now the Houston Ship Channel's outlet.

[4] Rising sea levels filled this tiny canyon first when the glacial era ended, followed by the vast lowlands of today's Trinity Bay.

[4] Between 7 and 5 thousand years ago, rapid sea-level rise moved the Gulf Coast northward to its current latitude.

[5] The plains are crossed by meandering streams that run southeast into the western Galveston Bay estuary and feature vast fresh and salty marshes.

[8] In addition, the bayous, rivers, and marshes that surround the bay maintain their own ecosystems, supporting a varied range of fauna and allowing freshwater crawfish farming.