i was watching a fishing show yesterday (forgot what it was) they were fishing for redfish and hooked up a decent sized largemouth.

do bass venture into brackish water?

Yes.

Bass can live in brackish water.

We have some creeks here in Virginia where you can catch LM bass and speckled trout in the same water.  

Over sustained periods of time, bass have a low tolerance for high salinity and high acidity (unlike chain pickerel).

The same is not true for red drum, who are highly tolerant fish, so it's more like red drum in bass territory.

Roger

Yes.

Bass can live in brackish water.

I didn't know that.  I learned my one thing for today. ;D

One of the private freshwater marshes in Southwest Louisiana had a huge influx of salt water during hurricane Rita 2 years ago and now is a killer location for catching huge numbers of both bass and redfish.  

When growing up in South Louisiana we fished the Biloxi marsh and when we tied up for the evening in the marsh we would fish for "green trout" which were largemouth bass.

I caught my first "green trout" on a spinning rig throwing a red and white spoon in the marsh.

I think I was about 12 years old.

Juvenile red drum, also known as puppy drum can stand lower levels of salinity. They are often caught in creeks where their is more fresh water.

Big T

I live in south louisiana and i have been on outings and on one cast I caught a bass then on the very next one caught a big red fish.  Its not unusual for that to happen around here and acctually there are a few areas that i know where i can go fishing for one and if that fish isnt biting, switch lures and catch the other.

T-Bone

The red drum, Sciaenops ocellatus, is a fish of many monikers. Most anglers in Texas and Louisiana call it "redfish," but some call it "channel bass" in parts of Florida, and "Pescado Colorado" or simply "Colorado" in Mexico. Redfish, also get names for different age classes. "Rat red" signifies juveniles whereas the term "bull red" applies to big, sexually mature specimens.

The species is fast growing, reaching approximately 11 inches and 1 pound in its first year, 17-22 inches and 3-1/2 pounds in two years, and 22-24 inches and 6-8 pounds in three years. The world record red drum weighed 96 pounds and hailed from the East Coast. The current Texas record is 55 pounds.

Texas Parks & Wildlife Department has successfully stocked them in several freshwater reservoirs including Fairfield, Braunig, and Calaveras. They cannot spawn in these lakes, but they grow to immense size and take to the habitat like, well, a fish takes to water. Instead of feeding on crab, they eat crawfish and terrorize the perch, shad, bass, and other wimpy freshwater species. Redfish are highly adaptable, and this allows them to survive in many habitats and live to great age.

In BPS here in Orlando they have both bass and reds in thier instore display tank.  Some bass are 8 lbs soem reds are bigger.  they also have a black drum.

The tidal portion of the Potomac is an excellent largemouth fishery. Although redfish aren't found that far north, you can catch several saltwater species as well as largeouth in the tidal Potomac.