Is the Gulf of Mexico composed of salt-water or fresh-water?

Fresh water. If you draw a line from Miami to Havana, everything east of the line is salt water and everything west of the line is fresh water. Great question.

The salt water of the ocean's is 35 parts per thousand (ppt); most of the Gulf of Mexico averages 28 to 32 ppt. However, some areas of the Gulf of Mexico average 36 ppt.

I would call that salt water.

Its a gulf of the Atlantic Ocean, which is Salt Water. All Oceans and Gulfs/Bays of the Oceans are Salt Water

The Gulf of Mexico is part of the Caribbean Sea which is part of the Atlantic Ocean and is therefore salt-water.

Salt

Salt water nucklehead all gulf's are salt water

I am sure all bodies of water that are connected to the oceans are composed of salt water.

Salt...the majority of its currents come from the Atlantic Sea which is obviously salt water

The salinity of the Gulf varies considerably because of the large amount of fresh water that flows into it from the Mississippi. You might check the USGS site to see whether they have any data on the relative salinity of different regions of the Gulf.

Salt.

Salt ocean water in bulk and slightly concentrated by evaporation; brackish where the Mississippi drains.